ref: 4e91e4a2dbab9d79e1047cfc2094a438561b5a21
dir: /sys/games/lib/sudoku/boards/medium-2005-05-25.su/
4...6.93. 7.2....1. ....43... 6..5..3.. .7.....8. ..5..9..7 ...29.... .9....2.8 .21.8...4 418762935 732958416 956143872 689527341 273416589 145839627 867294153 594371268 321685794