ref: c539d64d22a0fdef1bd044a6e28e02a6bcfd0adf
dir: /sys/games/lib/sudoku/boards/medium-2005-04-06.su/
..8.21.9. 3..4...2. ......3.5 .86..42.. ...8.3... ..92..65. 7.3...... .5...8..2 .2.53.4.. 568321794 317495826 942786315 186954273 275863149 439217658 793642581 654178932 821539467