ref: 5debddf8aff9cc647cd9eeb89c06a550fbf816e7
dir: /sys/games/lib/sudoku/boards/medium-2005-02-05.su/
..1...... 65....7.. 8..5.39.2 5..7.1..4 .4..3..9. 9..2.5..7 1.29.7..3 ..8....59 ......6.. 321879546 659124738 874563912 586791324 247638195 913245867 162957483 738416259 495382671