ref: 3d4d5940498dabb2c7abca2acd23a7e8be83e565
dir: /sys/games/lib/sudoku/boards/medium-2005-04-04.su/
2..6...9. 6....48.5 ..73....1 3.9...4.. ...1.6... ..4...5.7 5....82.. 8.17....4 .7...9..8 245681793 613974825 987325641 329857416 758146932 164293587 536418279 891762354 472539168