ref: ae61eb9381f6b0c70e1c52bf2c2b7f4cd0b5bb6f
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