ref: f596580cba7c5b7bae84ee7cd83d2b2a438a1e9b
dir: /sys/games/lib/sudoku/boards/hard-2005-03-27.su/
4..6213.. ...3...9. .8..9.... 6..1..8.. 35.....14 ..8..4..6 ....7..4. .3...9... ..5416..9 497621385 561348792 283795461 649152873 352867914 718934526 926573148 134289657 875416239