ref: ff8ae67b705129e20b4177aa4a0c85dab343e5bb
dir: /sys/games/lib/sudoku/boards/medium-2005-02-18.su/
649..3..1 .7....... ..37...45 13..8.... ...239... ....7..26 95...42.. .......5. 8..9..473 649523781 571648932 283791645 132486597 765239814 498175326 957314268 324867159 816952473