ref: 215b67ff3d630c56418026dda7ae68f23111c4a5
dir: /sys/games/lib/sudoku/boards/medium-2005-03-23.su/
.6.4..3.. 1983..... ..4.6..9. ..92..... 84.....29 .....75.. .2..7.9.. .....5813 ..5..6.7. 762489351 198352746 534761298 659248137 847513629 213697584 321874965 476925813 985136472