ref: ed3a576e8b103032b659febc5d3c62565c9cf7d7
dir: /sys/games/lib/sudoku/boards/hard-2005-04-07.su/
.7.6.5... 5..14.9.6 ..4.....2 4.....397 ......... 732.....4 2.....6.. 1.6.38..5 ...5.1.2. 973625148 528147936 614389752 461852397 859473261 732916584 285794613 196238475 347561829