ref: 5696c361a57a00286c1eee148b51c39f6a265f53
dir: /sys/games/lib/sudoku/boards/medium-2005-04-29.su/
5.1....7. ..94....2 .6..1.9.8 ...1..784 ......... 254..6... 4.5.7..3. 1....24.. .9....1.5 541298673 879463512 362517948 936125784 718349256 254786391 425671839 183952467 697834125