ref: c6ae349e9d67ef24ce429f699c5232a9acdcb1ea
dir: /sys/games/lib/sudoku/boards/medium-2005-02-21.su/
.....94.. ...2.8..7 47..1.3.. 5.9..6..2 ..8...1.. 3..5..8.9 ..5.9..81 8..3.2... ..48..... 186739425 953248617 472615398 549186732 768923154 321574869 635497281 817352946 294861573