ref: fbf9f131b5931defb02ff08d54d1e088d9f51a15
dir: /sys/games/lib/sudoku/boards/hard-2005-04-17.su/
6........ ...1..97. .9..4.1.2 3..9...16 ...435... 24...1..8 4.5.7..2. .26..3... ........5 612397584 584126973 793548162 357982416 861435297 249761358 435679821 126853749 978214635