ref: cb1555c7d741fa482c339aa9ac8a44753e2ad296
dir: /sys/games/lib/sudoku/boards/medium-2005-03-01.su/
9....1... .....62.8 .15.8.... .5..398.. .49...67. ..387..2. ....1.76. 3.89..... ...2....9 986421537 437596218 215783496 752639841 849152673 163874925 594318762 328967154 671245389