ref: a4ab99da40e0e86aa61d145e038066e8210c27a9
dir: /sys/games/lib/sudoku/boards/medium-2005-04-19.su/
...5746.. ...8...54 ..5...... 96..5.4.. 2.......8 ..8.6..31 ......1.. 72...6... ..1397... 182574693 396821754 475639812 963158427 217943568 548762931 634285179 729416385 851397246