Introduction - If you have any usage issues, please Google them yourself
Set cover problem: in a 2k × 2k grid consisting of a chessboard, just have a box with other boxes is different from that of the grid is a special box, and said the board is a special board. Coverage in the chessboard problems, the four kinds of icons to use different forms of L-type domino coverage given special chessboard except in special box outside the grid of all, and any two L-type domino coverage shall not overlap.