Y by Adventure10
There are
pieces on the squares of a
board, at most one on each square at any time during the game. A move in the game consists of simultaneously moving each piece to a neighboring square by side, under the restriction that a piece having been moved horizontally in the previous move must be moved vertically and vice versa. Find the greatest value of
for which there exists an initial position starting at which the game can be continued until the end of the world.


