ref: bf2a6f786502026ce4229bc84a6a22e5e55a7c13
dir: /sys/games/lib/sudoku/boards/medium-2005-03-16.su/
..3.2...5 ...3.8.1. ..154..9. 2..15.... .6.....7. ....64..2 .1..728.. .2.8.9... 4...1.9.. 943721685 652398714 871546293 294157368 165283479 387964152 519472836 726839541 438615927