ref: 882ec4ba3d42f15e630119e1f43e5400123539b5
dir: /sys/games/lib/sudoku/boards/easy-2005-02-12.su/
.28..3... 9.4.6...2 36..92... 1....698. ......... .972....5 ...62..57 7...1.2.9 ...8..13. 528173694 974568312 361492578 142756983 635984721 897231465 413629857 786315249 259847136