Four-Three Check chess

[lkaufman]

The variant "3 check chess" (where normal chess rules apply but giving check 3 times total is also a win) seems to be reasonably popular on chess.com and LiChess, with MVL apparently the best player and quite a fan of the variant. Presumably it has hardly any draws, but at least at the engine level it is not a playable game due to overwhelming White advantage. I ran 500 games overnight on 4 threads (to get variety) using Fairy Stockfish, at 2' + 1" level, and got a result of +477 -9 =14, a 592 elo advantage for White. Of course between humans it wouldn't be this lopsided, but clearly the game is a win for White, and is too unbalanced to take seriously.

However it occurred to me that if we require White to give 4 checks to win, while Black needs only 3, it might be roughly fair; at least it isn't obvious which side has the advantage. I would pick Black if I had to choose, but I might be wrong, and most likely it would not be a grossly one-sided game. So my question is, has anyone tested this "4-3 check chess" variant (I imagine I'm not the first to think of it), and is there any reason to think that this would not be much closer to balanced than the 3 check variant? I suppose if the 3 check version of Fairy Stockfish were used to test this variant, it wouldn't play it so well with the 3 check weights, but at least it might tell whether the idea had merit.

[Ajedrecista]

Hello Larry:

The variant "3 check chess" (where normal chess rules apply but giving check 3 times total is also a win) seems to be reasonably popular on chess.com and LiChess, with MVL apparently the best player and quite a fan of the variant. Presumably it has hardly any draws, but at least at the engine level it is not a playable game due to overwhelming White advantage. I ran 500 games overnight on 4 threads (to get variety) using Fairy Stockfish, at 2' + 1" level, and got a result of +477 -9 =14, a 592 elo advantage for White. Of course between humans it wouldn't be this lopsided, but clearly the game is a win for White, and is too unbalanced to take seriously.

However it occurred to me that if we require White to give 4 checks to win, while Black needs only 3, it might be roughly fair; at least it isn't obvious which side has the advantage. I would pick Black if I had to choose, but I might be wrong, and most likely it would not be a grossly one-sided game. So my question is, has anyone tested this "4-3 check chess" variant (I imagine I'm not the first to think of it), and is there any reason to think that this would not be much closer to balanced than the 3 check variant? I suppose if the 3 check version of Fairy Stockfish were used to test this variant, it wouldn't play it so well with the 3 check weights, but at least it might tell whether the idea had merit.

You might also think the other way: what about 1-check? Are we able to determine a winning side, i.e. a forced check for a side under X moves? Then go for 2-check and finally a generalization of n-check. 3-check looks enough difficult to try to solve, imagine 4-check. OTOH, 1-check could be tried and who knows, maybe someone can proof a forced sequence, something like giveaway chess.

Regards from Spain.

Ajedrecista.

[lkaufman]

Hello Larry:

The variant "3 check chess" (where normal chess rules apply but giving check 3 times total is also a win) seems to be reasonably popular on chess.com and LiChess, with MVL apparently the best player and quite a fan of the variant. Presumably it has hardly any draws, but at least at the engine level it is not a playable game due to overwhelming White advantage. I ran 500 games overnight on 4 threads (to get variety) using Fairy Stockfish, at 2' + 1" level, and got a result of +477 -9 =14, a 592 elo advantage for White. Of course between humans it wouldn't be this lopsided, but clearly the game is a win for White, and is too unbalanced to take seriously.

However it occurred to me that if we require White to give 4 checks to win, while Black needs only 3, it might be roughly fair; at least it isn't obvious which side has the advantage. I would pick Black if I had to choose, but I might be wrong, and most likely it would not be a grossly one-sided game. So my question is, has anyone tested this "4-3 check chess" variant (I imagine I'm not the first to think of it), and is there any reason to think that this would not be much closer to balanced than the 3 check variant? I suppose if the 3 check version of Fairy Stockfish were used to test this variant, it wouldn't play it so well with the 3 check weights, but at least it might tell whether the idea had merit.

You might also think the other way: what about 1-check? Are we able to determine a winning side, i.e. a forced check for a side under X moves? Then go for 2-check and finally a generalization of n-check. 3-check looks enough difficult to try to solve, imagine 4-check. OTOH, 1-check could be tried and who knows, maybe someone can proof a forced sequence, something like giveaway chess.

Regards from Spain.

Ajedrecista.

Hello Larry:

The variant "3 check chess" (where normal chess rules apply but giving check 3 times total is also a win) seems to be reasonably popular on chess.com and LiChess, with MVL apparently the best player and quite a fan of the variant. Presumably it has hardly any draws, but at least at the engine level it is not a playable game due to overwhelming White advantage. I ran 500 games overnight on 4 threads (to get variety) using Fairy Stockfish, at 2' + 1" level, and got a result of +477 -9 =14, a 592 elo advantage for White. Of course between humans it wouldn't be this lopsided, but clearly the game is a win for White, and is too unbalanced to take seriously.

However it occurred to me that if we require White to give 4 checks to win, while Black needs only 3, it might be roughly fair; at least it isn't obvious which side has the advantage. I would pick Black if I had to choose, but I might be wrong, and most likely it would not be a grossly one-sided game. So my question is, has anyone tested this "4-3 check chess" variant (I imagine I'm not the first to think of it), and is there any reason to think that this would not be much closer to balanced than the 3 check variant? I suppose if the 3 check version of Fairy Stockfish were used to test this variant, it wouldn't play it so well with the 3 check weights, but at least it might tell whether the idea had merit.

You might also think the other way: what about 1-check? Are we able to determine a winning side, i.e. a forced check for a side under X moves? Then go for 2-check and finally a generalization of n-check. 3-check looks enough difficult to try to solve, imagine 4-check. OTOH, 1-check could be tried and who knows, maybe someone can proof a forced sequence, something like giveaway chess.

Regards from Spain.

Ajedrecista.

1-check should be pretty easy to prove as a forced win for White, with a suitable engine, perhaps someone has already done this? I don't expect that it will be practical to prove that 3 check is a forced win for White, any more than it is practical to prove that knight odds standard chess is a forced win for Black, but both claims are almost certainly true, based on the overwhelming stats from engine play. My point is not that 3 check is provably a win, but that it is empirically so winning that it is unplayable between engines without some tweak such as the 4-3 tweak I suggest.

[Ajedrecista]

Hello:

1-check should be pretty easy to prove as a forced win for White, with a suitable engine, perhaps someone has already done this? I don't expect that it will be practical to prove that 3 check is a forced win for White, any more than it is practical to prove that knight odds standard chess is a forced win for Black, but both claims are almost certainly true, based on the overwhelming stats from engine play. My point is not that 3 check is provably a win, but that it is empirically so winning that it is unplayable between engines without some tweak such as the 4-3 tweak I suggest.

I think I already got your point before my first reply: that 3-check is very loopsided and 4-check should be more fair. I would say that my n-check generalization holds: when n is unbound, you get normal chess; with low n, the game gets more and more unfair or loopsided. My 1-check proposal was a challenge if anyone is interested.

Plot twist: I really misunderstood you. I thought that you proposed to raise the thresold to four checks for both white and black, when you really proposed asymmetric thresolds (4 for white and 3 for black). Then my generalization evolves to {n,m} and more possibilities, with the {1,1} challenge still alive just for curiosity.

Where is the point of a balanced game? {3,2}, {4,3}, {5,3}, {5,4}, ...? In other words: how much is worth a check with the rest of the rules valid (e.g. checkmate, usually through material advantage, specially if a side throws material in order to give checks and approach its thresold). Interesting question, indeed.

Regards from Spain.

Ajedrecista.

[hgm]

Isn't it a bit suspect that the first-move advantage would be so large? Such an imbalance would suggest the initial position is not tactically quiet. Is it known what exactly is the problem for black?

How was this measured anyway? Does Stockfish randomize? Or was an opening book used? If so, how do we know the problem is not in the book?

I have never played this variant, but I have some experience with another variant that hardly be callled tactically quiet: Tenjiku Shogi. There white gets an enormously dangerous attack, but when black finds the unique adequate defence it can still achieve approximate equalty. That almost any deviation by black is losing doesn't help white win the game when black knows the line. But an opening book can easily destroy that.

[Uri Blass]

Hello Larry:

The variant "3 check chess" (where normal chess rules apply but giving check 3 times total is also a win) seems to be reasonably popular on chess.com and LiChess, with MVL apparently the best player and quite a fan of the variant. Presumably it has hardly any draws, but at least at the engine level it is not a playable game due to overwhelming White advantage. I ran 500 games overnight on 4 threads (to get variety) using Fairy Stockfish, at 2' + 1" level, and got a result of +477 -9 =14, a 592 elo advantage for White. Of course between humans it wouldn't be this lopsided, but clearly the game is a win for White, and is too unbalanced to take seriously.

However it occurred to me that if we require White to give 4 checks to win, while Black needs only 3, it might be roughly fair; at least it isn't obvious which side has the advantage. I would pick Black if I had to choose, but I might be wrong, and most likely it would not be a grossly one-sided game. So my question is, has anyone tested this "4-3 check chess" variant (I imagine I'm not the first to think of it), and is there any reason to think that this would not be much closer to balanced than the 3 check variant? I suppose if the 3 check version of Fairy Stockfish were used to test this variant, it wouldn't play it so well with the 3 check weights, but at least it might tell whether the idea had merit.

You might also think the other way: what about 1-check? Are we able to determine a winning side, i.e. a forced check for a side under X moves? Then go for 2-check and finally a generalization of n-check. 3-check looks enough difficult to try to solve, imagine 4-check. OTOH, 1-check could be tried and who knows, maybe someone can proof a forced sequence, something like giveaway chess.

Regards from Spain.

Ajedrecista.

Hello Larry:

The variant "3 check chess" (where normal chess rules apply but giving check 3 times total is also a win) seems to be reasonably popular on chess.com and LiChess, with MVL apparently the best player and quite a fan of the variant. Presumably it has hardly any draws, but at least at the engine level it is not a playable game due to overwhelming White advantage. I ran 500 games overnight on 4 threads (to get variety) using Fairy Stockfish, at 2' + 1" level, and got a result of +477 -9 =14, a 592 elo advantage for White. Of course between humans it wouldn't be this lopsided, but clearly the game is a win for White, and is too unbalanced to take seriously.

However it occurred to me that if we require White to give 4 checks to win, while Black needs only 3, it might be roughly fair; at least it isn't obvious which side has the advantage. I would pick Black if I had to choose, but I might be wrong, and most likely it would not be a grossly one-sided game. So my question is, has anyone tested this "4-3 check chess" variant (I imagine I'm not the first to think of it), and is there any reason to think that this would not be much closer to balanced than the 3 check variant? I suppose if the 3 check version of Fairy Stockfish were used to test this variant, it wouldn't play it so well with the 3 check weights, but at least it might tell whether the idea had merit.

You might also think the other way: what about 1-check? Are we able to determine a winning side, i.e. a forced check for a side under X moves? Then go for 2-check and finally a generalization of n-check. 3-check looks enough difficult to try to solve, imagine 4-check. OTOH, 1-check could be tried and who knows, maybe someone can proof a forced sequence, something like giveaway chess.

Regards from Spain.

Ajedrecista.

1-check should be pretty easy to prove as a forced win for White, with a suitable engine, perhaps someone has already done this? I don't expect that it will be practical to prove that 3 check is a forced win for White, any more than it is practical to prove that knight odds standard chess is a forced win for Black, but both claims are almost certainly true, based on the overwhelming stats from engine play. My point is not that 3 check is provably a win, but that it is empirically so winning that it is unplayable between engines without some tweak such as the 4-3 tweak I suggest.

I tried to prove by a tree that I generate that 1.e4 is winning in 1-check without an engine(I suspect that it may be easy enough for humans to solve it without an engine).
This is what I found:

1.e4 e5 2.Qh5 and g6 is the only way to defend against 3.Qxf7+ but does not prevent Qxe5+ so 1...e5 is losing.
1.e4 e6 2.Qh5 g6(only way to defend against 3.Qxf7+) 3.Qe5(threat Qxe6+)
possible replies to prevent the check are Ne7 Be7 Qe7 but all lose
3...Ne7 4.Qf6 and it is impossible to prevent 5.Qxf7+
3...Be7 4.Qg7 and no defence against 5.Qxf7+ or Qf8+
3...Qe7 4.Qxc7 and no defence against 5.Qxd7+ or Qd8+
so 1...e6 is also losing

1.e4 a6(or a5 or b6 or b5 or c6 or c5 or h6 or Nh6 or Na6) 2.Qh5 g6 only defence 3.Qe5 and I see no defence against Qxe7+ except e6 that allow Qxe6+
1.e4 d6(d5) 2.Bb5+
1.e4 f6(f5) 2.Qh5+
1.e4 g5 2,Qh5 and no defenct against 3.Qxf7+
1.e4 Nc6 2.Qh5 g6 3.Qc5 and I see no defence against 4.Qxe7+ or if d6 4.Qxc6+
only defences to refute 1....g6 1...h5 1...Nf6

[lkaufman]

Hello Larry:

The variant "3 check chess" (where normal chess rules apply but giving check 3 times total is also a win) seems to be reasonably popular on chess.com and LiChess, with MVL apparently the best player and quite a fan of the variant. Presumably it has hardly any draws, but at least at the engine level it is not a playable game due to overwhelming White advantage. I ran 500 games overnight on 4 threads (to get variety) using Fairy Stockfish, at 2' + 1" level, and got a result of +477 -9 =14, a 592 elo advantage for White. Of course between humans it wouldn't be this lopsided, but clearly the game is a win for White, and is too unbalanced to take seriously.

However it occurred to me that if we require White to give 4 checks to win, while Black needs only 3, it might be roughly fair; at least it isn't obvious which side has the advantage. I would pick Black if I had to choose, but I might be wrong, and most likely it would not be a grossly one-sided game. So my question is, has anyone tested this "4-3 check chess" variant (I imagine I'm not the first to think of it), and is there any reason to think that this would not be much closer to balanced than the 3 check variant? I suppose if the 3 check version of Fairy Stockfish were used to test this variant, it wouldn't play it so well with the 3 check weights, but at least it might tell whether the idea had merit.

You might also think the other way: what about 1-check? Are we able to determine a winning side, i.e. a forced check for a side under X moves? Then go for 2-check and finally a generalization of n-check. 3-check looks enough difficult to try to solve, imagine 4-check. OTOH, 1-check could be tried and who knows, maybe someone can proof a forced sequence, something like giveaway chess.

Regards from Spain.

Ajedrecista.

Hello Larry:

The variant "3 check chess" (where normal chess rules apply but giving check 3 times total is also a win) seems to be reasonably popular on chess.com and LiChess, with MVL apparently the best player and quite a fan of the variant. Presumably it has hardly any draws, but at least at the engine level it is not a playable game due to overwhelming White advantage. I ran 500 games overnight on 4 threads (to get variety) using Fairy Stockfish, at 2' + 1" level, and got a result of +477 -9 =14, a 592 elo advantage for White. Of course between humans it wouldn't be this lopsided, but clearly the game is a win for White, and is too unbalanced to take seriously.

However it occurred to me that if we require White to give 4 checks to win, while Black needs only 3, it might be roughly fair; at least it isn't obvious which side has the advantage. I would pick Black if I had to choose, but I might be wrong, and most likely it would not be a grossly one-sided game. So my question is, has anyone tested this "4-3 check chess" variant (I imagine I'm not the first to think of it), and is there any reason to think that this would not be much closer to balanced than the 3 check variant? I suppose if the 3 check version of Fairy Stockfish were used to test this variant, it wouldn't play it so well with the 3 check weights, but at least it might tell whether the idea had merit.

You might also think the other way: what about 1-check? Are we able to determine a winning side, i.e. a forced check for a side under X moves? Then go for 2-check and finally a generalization of n-check. 3-check looks enough difficult to try to solve, imagine 4-check. OTOH, 1-check could be tried and who knows, maybe someone can proof a forced sequence, something like giveaway chess.

Regards from Spain.

Ajedrecista.

1-check should be pretty easy to prove as a forced win for White, with a suitable engine, perhaps someone has already done this? I don't expect that it will be practical to prove that 3 check is a forced win for White, any more than it is practical to prove that knight odds standard chess is a forced win for Black, but both claims are almost certainly true, based on the overwhelming stats from engine play. My point is not that 3 check is provably a win, but that it is empirically so winning that it is unplayable between engines without some tweak such as the 4-3 tweak I suggest.

I tried to prove by a tree that I generate that 1.e4 is winning in 1-check without an engine(I suspect that it may be easy enough for humans to solve it without an engine).
This is what I found:

1.e4 e5 2.Qh5 and g6 is the only way to defend against 3.Qxf7+ but does not prevent Qxe5+ so 1...e5 is losing.
1.e4 e6 2.Qh5 g6(only way to defend against 3.Qxf7+) 3.Qe5(threat Qxe6+)
possible replies to prevent the check are Ne7 Be7 Qe7 but all lose
3...Ne7 4.Qf6 and it is impossible to prevent 5.Qxf7+
3...Be7 4.Qg7 and no defence against 5.Qxf7+ or Qf8+
3...Qe7 4.Qxc7 and no defence against 5.Qxd7+ or Qd8+
so 1...e6 is also losing

1.e4 a6(or a5 or b6 or b5 or c6 or c5 or h6 or Nh6 or Na6) 2.Qh5 g6 only defence 3.Qe5 and I see no defence against Qxe7+ except e6 that allow Qxe6+
1.e4 d6(d5) 2.Bb5+
1.e4 f6(f5) 2.Qh5+
1.e4 g5 2,Qh5 and no defenct against 3.Qxf7+
1.e4 Nc6 2.Qh5 g6 3.Qc5 and I see no defence against 4.Qxe7+ or if d6 4.Qxc6+
only defences to refute 1....g6 1...h5 1...Nf6

Yes, I thought of several of these lines without even looking at a board, I imagined it would be pretty easy to prove a forced win for White in 1-check, as you have shown. Two-check would almost certainly require deep analysis with an appropriate engine to prove the win, while three-check is probably unprovable in any practical amount of time.

[lkaufman]

Isn't it a bit suspect that the first-move advantage would be so large? Such an imbalance would suggest the initial position is not tactically quiet. Is it known what exactly is the problem for black?

How was this measured anyway? Does Stockfish randomize? Or was an opening book used? If so, how do we know the problem is not in the book?

I have never played this variant, but I have some experience with another variant that hardly be callled tactically quiet: Tenjiku Shogi. There white gets an enormously dangerous attack, but when black finds the unique adequate defence it can still achieve approximate equalty. That almost any deviation by black is losing doesn't help white win the game when black knows the line. But an opening book can easily destroy that.

For variety I relied on MP (4) variability. Although not ideal, I think it was enough to prove the point, as I saw many defenses to 1.e4 being chosen, even on move 1. The 97% White score is higher than I would have guessed, but not way higher, since White generally shows evals like +2 or so after a few moves. Getting in the first check is worth nearly a minor piece according to the eval of the engine used, so Black must play very cautiously (or gambit pawns) to avoid any non-piece losing check. So even if he avoids an early check, he gets a very cramped and/or pawn down position, which is normally losing even in normal chess.

After thinking about this a bit, it seems likely to me that my proposed 4-3 check would favor Black considerably, perhaps less than 3 check favors White, but still too much. Black could play boldly, allowing the first check, and still be favored if he is then in the best position to make the next check. Maybe 5-4 would be more balanced. Note that 5 check is a practical maximum if the goal is to avoid most draws, since the typical direct perpetual check would mean giving five checks, so a 6 check rule would fail to stop all perpetual checks. I think that 5-check (which is a known variant though much less popular than 3-check) would probably not give White anywhere near the edge he has in 3-check, since the value of getting in the first check would be dramatically lower, maybe below a pawn, so Black could probably play some decent normal defense (perhaps the Sicilian Kan would be a good choice). In other words, 3-check doesn't seem much like normal chess, but 5-check probably feels more like normal chess with a tie-breaking rule added. Perhaps five-check Armageddon (Black wins draws) would be reasonably fair, although I would bet on White. But I don't know of any engine that has been optimized for five-check to test this hypothesis.

[hgm]

For variety I relied on MP (4) variability. Although not ideal, I think it was enough to prove the point, as I saw many defenses to 1.e4 being chosen, even on move 1. The 97% White score is higher than I would have guessed, but not way higher, since White generally shows evals like +2 or so after a few moves. Getting in the first check is worth nearly a minor piece according to the eval of the engine used, so Black must play very cautiously (or gambit pawns) to avoid any non-piece losing check. So even if he avoids an early check, he gets a very cramped and/or pawn down position, which is normally losing even in normal chess.

If there is a winning score so early in the game this points to an opening problem. It doesn't excluse that careful study of opening theory could reveal a line through which black can equalize. Even a very long analysis search with a top engine is not very good at distinguishing good from poor opening lines, as the engine has the tendency of confirming its own strategic misconceptions. At short TC the engine would never see it is running into a trap before it is too late. So if loosing lines are plentiful, and good defense is just a narrow path (as was the case in Tenjiku Shogi), stumbling along blindly will give an unrepresentative result.

After thinking about this a bit, it seems likely to me that my proposed 4-3 check would favor Black considerably, perhaps less than 3 check favors White, but still too much. Black could play boldly, allowing the first check, and still be favored if he is then in the best position to make the next check. Maybe 5-4 would be more balanced. Note that 5 check is a practical maximum if the goal is to avoid most draws, since the typical direct perpetual check would mean giving five checks, so a 6 check rule would fail to stop all perpetual checks. I think that 5-check (which is a known variant though much less popular than 3-check) would probably not give White anywhere near the edge he has in 3-check, since the value of getting in the first check would be dramatically lower, maybe below a pawn, so Black could probably play some decent normal defense (perhaps the Sicilian Kan would be a good choice). In other words, 3-check doesn't seem much like normal chess, but 5-check probably feels more like normal chess with a tie-breaking rule added. Perhaps five-check Armageddon (Black wins draws) would be reasonably fair, although I would bet on White. But I don't know of any engine that has been optimized for five-check to test this hypothesis.

It doesn't seem likely that merely 'thinking about it' would be a successful method for getting at the truth. The 4-3 thing (or any other 'checks odds') must be easy to test. Just let Fairy-Stockfish play 4-checks from a start position with an unbalanced number of checks.

[lkaufman]

For variety I relied on MP (4) variability. Although not ideal, I think it was enough to prove the point, as I saw many defenses to 1.e4 being chosen, even on move 1. The 97% White score is higher than I would have guessed, but not way higher, since White generally shows evals like +2 or so after a few moves. Getting in the first check is worth nearly a minor piece according to the eval of the engine used, so Black must play very cautiously (or gambit pawns) to avoid any non-piece losing check. So even if he avoids an early check, he gets a very cramped and/or pawn down position, which is normally losing even in normal chess.

If there is a winning score so early in the game this points to an opening problem. It doesn't excluse that careful study of opening theory could reveal a line through which black can equalize. Even a very long analysis search with a top engine is not very good at distinguishing good from poor opening lines, as the engine has the tendency of confirming its own strategic misconceptions. At short TC the engine would never see it is running into a trap before it is too late. So if loosing lines are plentiful, and good defense is just a narrow path (as was the case in Tenjiku Shogi), stumbling along blindly will give an unrepresentative result.

After thinking about this a bit, it seems likely to me that my proposed 4-3 check would favor Black considerably, perhaps less than 3 check favors White, but still too much. Black could play boldly, allowing the first check, and still be favored if he is then in the best position to make the next check. Maybe 5-4 would be more balanced. Note that 5 check is a practical maximum if the goal is to avoid most draws, since the typical direct perpetual check would mean giving five checks, so a 6 check rule would fail to stop all perpetual checks. I think that 5-check (which is a known variant though much less popular than 3-check) would probably not give White anywhere near the edge he has in 3-check, since the value of getting in the first check would be dramatically lower, maybe below a pawn, so Black could probably play some decent normal defense (perhaps the Sicilian Kan would be a good choice). In other words, 3-check doesn't seem much like normal chess, but 5-check probably feels more like normal chess with a tie-breaking rule added. Perhaps five-check Armageddon (Black wins draws) would be reasonably fair, although I would bet on White. But I don't know of any engine that has been optimized for five-check to test this hypothesis.

It doesn't seem likely that merely 'thinking about it' would be a successful method for getting at the truth. The 4-3 thing (or any other 'checks odds') must be easy to test. Just let Fairy-Stockfish play 4-checks from a start position with an unbalanced number of checks.

Using CuteChess, I can set Fairy-Stockfish to play 3-check or 5-check; there is no option for 4-check. But it seems that if I set it to play 5-check it plays more or less as if it is normal chess, it doesn't seem to try to play an early check the way it does at 3-check. So I don't know how valid a test would be starting with 5-check (with some checks already played). Does anyone know anything about this? Also if the checks are played to get to the start position, they may not count towards the total, I don't know about that. I suppose I could use a start position where the side to move has an obvious safe check. So that might allow for a test of 5-4 check.