ref: 7a8e875668d92020548d07b5ad30f7b83b61d1fc
dir: /sys/games/lib/sudoku/boards/hard-2005-04-17.su/
6........ ...1..97. .9..4.1.2 3..9...16 ...435... 24...1..8 4.5.7..2. .26..3... ........5 612397584 584126973 793548162 357982416 861435297 249761358 435679821 126853749 978214635