ref: 1d94a18e5683d0d69aca4c8350b7914419fae6bc
dir: /sys/games/lib/sudoku/boards/medium-2005-05-27.su/
....28369 .29.3.... ...1....8 ..8...1.. 9.3...8.4 ..1...9.. 4....7... ....5.41. 38624.... 157428369 829635741 634179258 278964135 963512874 541783926 415397682 792856413 386241597