ref: b9d26a293eec4be3e9c46b6ce40d01a61646b8b8
dir: /sys/games/lib/sudoku/boards/medium-2005-02-22.su/
..41.9... 9.6...... 23..4..8. .51....9. 3..8.5..7 .4....26. .7..1..23 ......8.1 ...5.79.. 784159632 916283754 235746189 651472398 392865417 847391265 479618523 563924871 128537946