ref: 7c1e0be91969ab0d8fca4bd1fd52de32f4a9a0c5
dir: /sys/games/lib/sudoku/boards/medium-2005-03-18.su/
...1254.. ..84..... 42.8..... .3.....95 .6.9.2.1. 51.....6. .....3.49 .....72.. ..1298... 976125438 158436927 423879156 234761895 867952314 519384762 782513649 395647281 641298573