ref: ca796cf5afa68acef4f73b7572c6f167dee6227d
dir: /sys/games/lib/sudoku/boards/hard-2005-04-22.su/
9..7....4 .4..3.... ..2..6.3. ..7.....6 6.92.74.3 8.....7.. .5.3..9.. ....6..5. 2....5..1 963718524 145932678 782546139 537184296 619257483 824693715 458321967 371469852 296875341