ref: b7a4dab54ab89f9cd62f3a31166cff553450cd28
dir: /sys/games/lib/sudoku/boards/medium-2005-02-26.su/
..3..1..9 94...72.3 ..8..9.7. ....75... 7.......4 ...24.... .1.8..6.. 6.97...42 2..6..5.. 573421869 946587213 128369475 864975321 752136984 391248756 415892637 689753142 237614598