ref: 6efabda4863a13cf811575e5dbde9e33ef91c8cf
dir: /sys/games/lib/sudoku/boards/easy-2005-02-09.su/
9.....164 8...4..5. ...1.9.7. .....23.6 .4.8.3.2. 3.25..... .1.3.5... .2..9...8 659.....2 975238164 831647259 264159873 587912346 146873925 392564781 418325697 723496518 659781432