ref: b9d26a293eec4be3e9c46b6ce40d01a61646b8b8
dir: /sys/games/lib/sudoku/boards/medium-2005-04-05.su/
17.5.2... .53..1..7 ..69....2 .....8.4. .6.....3. .4.3..... 7....39.. 8..7..52. ...2.4.13 179542368 253861497 486937152 327198645 968475231 541326879 712653984 834719526 695284713