ref: 152159a8297a7595b4455c03361851d354288177
dir: /sys/games/lib/sudoku/boards/hard-2005-05-07.su/
58...7... ..645.8.. ..7.3...1 1....9.2. 8.......6 .6.2....4 7...9.2.. ..1.239.. ...8...13 589617432 316452879 427938561 154769328 872345196 963281754 738196245 641523987 295874613