ref: 3e7d71878bbb318a3774a2b5a75965e41e6a4a43
dir: /sys/games/lib/sudoku/boards/easy-2005-02-17.su/
4..2..3.. .8.94.7.. ..67..45. .29..5... 3..4.7..9 ...3..52. .93..46.. ..5.69.4. ..8..2..5 417256398 582943716 936718452 729685134 351427869 864391527 293574681 175869243 648132975