ref: 0f50c54b5ec2c8d2ca681021deaedc0cffdf7f1a
dir: /sys/games/lib/sudoku/boards/medium-2005-03-22.su/
.7...54.. 1.5.3.... .6.81..73 7......6. ..2...3.. .1......2 98..72.3. ....9.2.1 ..16...8. 378925416 145736928 269814573 753289164 892461357 416357892 984172635 637598241 521643789