ref: 5f7a6b7ea3c4ae1b51beffe3309e9b6b0491e71f
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