ref: 8188b4f4f0e07b6669e6ae3c6c1099af917eaab4
dir: /sys/games/lib/sudoku/boards/hard-2005-03-19.su/
..19....3 9..7..16. .3...5..7 .5......9 ..43.26.. 2......7. 6..1...3. .42..7..6 5....68.. 761928453 925743168 438615927 357461289 894372615 216589374 689154732 142837596 573296841