ref: d5821ae5517a14a33d59b742f544e7de7afd238f
dir: /sys/games/lib/sudoku/boards/hard-2005-05-22.su/
..6..2... ....5.4.2 .7.49..1. 7.4..92.. 1.......8 ..91..5.3 .1..46.5. 6.5.7.... ...5..3.. 546312897 981657432 273498615 754839261 132765948 869124573 318246759 625973184 497581326