ref: b51d7ca3bacb341dc96f1586b927b1770f05342e
dir: /sys/games/lib/sudoku/boards/medium-2005-02-28.su/
.4.5.7... .1..3.4.2 ...2.83.. 2.....836 ......... 761.....4 ..68.3... 4.9.2..5. ...1.4.8. 342517968 815639472 697248315 254971836 938465721 761382594 176853249 489726153 523194687