ref: f341ae8c777dda2876beb4d4a1c67c4e920595ca
dir: /sys/games/lib/sudoku/boards/easy-2005-03-05.su/
...31..28 .45....9. .3..8...7 3...512.. 9.......5 ..297...4 4...3..1. .2....85. 18..96... 796315428 845762391 231489567 364851279 978624135 512973684 457238916 629147853 183596742