ref: 9429dd64f746ebf9afc634f50f3f88d9408cfa7e
dir: /sys/games/lib/sudoku/boards/hard-2005-04-30.su/
1.....5.. .562.4... .2.1..3.. .9..51..4 7.......5 8..32..1. ..7..6.5. ...5.216. ..9.....3 178963542 356274891 924185376 692851734 731649285 845327619 217436958 483592167 569718423