ref: b9d26a293eec4be3e9c46b6ce40d01a61646b8b8
dir: /sys/games/lib/sudoku/boards/easy-2005-02-13.su/
.3..4.7.. ..8.9..56 ..2..613. 2..8....5 1..372..4 3....9..7 .531..8.. 82..3.6.. ..1.2..4. 936541728 718293456 542786139 297814365 165372984 384659217 453167892 829435671 671928543