ref: 02b867f01eca1fefbe8b29205c8a8d4c13d2ffd0
dir: /sys/games/lib/sudoku/boards/medium-2005-03-30.su/
.2..67..1 ..63...4. ...1..5.2 .1......6 4..678..9 6......8. 7.5..3... .4...68.. 8..94..2. 524867931 196352748 387194562 218539476 453678219 679421385 765283194 942716853 831945627