ref: 06ac3cf30beeb3a284ac9f6d23c4121036355c10
dir: /sys/games/lib/sudoku/boards/medium-2005-03-02.su/
5...98... ..6.4.9.. 4.81.6.7. 2........ 3.9...1.5 ........6 .4.5.13.2 ..3.7.8.. ...23...1 532798614 716345928 498126573 261853497 379462185 854917236 947581362 123674859 685239741