ref: 85afec4c2f95f12970b9f0e9a73a02cf29645745
dir: /sys/games/lib/sudoku/boards/medium-2005-02-19.su/
5....921. 8.7.52... .3...1... ..4....8. .53.1.94. .8....6.. ...4...3. ...16.8.2 .219....6 546739218 817652394 932841765 274396581 653218947 189574623 768425139 495163872 321987456