ref: 3e7d71878bbb318a3774a2b5a75965e41e6a4a43
dir: /sys/games/lib/sudoku/boards/medium-2005-02-20.su/
.9.....35 ..5..3... 34.6..9.. ...5.47.6 ..7...3.. 6.41.9... ..2..6.13 ...2..5.. 16.....8. 796428135 825913674 341657928 218534796 957862341 634179852 582796413 473281569 169345287