ref: 29d22d1362241e8688f99c06416300cb3431ba61
dir: /sys/games/lib/sudoku/boards/hard-2005-04-08.su/
....7.... .6.8.4.3. 8.....62. ...2.1..7 1.3...8.5 9..5.8... .94.....6 .5.1.9.8. ....4.... 439672518 562814739 871953624 685291347 123467895 947538261 294385176 756129483 318746952