ref: e969575d2e55eec89d3a2765b974e023123d8fa5
dir: /sys/games/lib/sudoku/boards/easy-2005-05-24.su/
...3..2.. 4.7....5. 2..1.79.. .4..7..23 .7.8.5.4. 96..3..7. ..96.2..5 .2....7.6 ..4..9... 516394287 497268351 283157964 845976123 371825649 962431578 739682415 128543796 654719832