ref: 1de9ca2de54d8f57557c4a4fa5994bac8ddec2fd
dir: /sys/games/lib/sudoku/boards/medium-2005-05-09.su/
..2...... .7....15. .3..95.8. ....1..49 ..17.45.. 34..6.... .9.27..6. .24....9. ......7.. 512847936 879326154 436195287 287513649 961784523 345962871 193278465 724651398 658439712