ref: 375d8f437013d0d5106e6c8c6d8dd79db6de456a
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