ref: dc96f164a2b72ccb209ae98ce50a11087cbe44f8
dir: /sys/games/lib/sudoku/boards/medium-2005-05-02.su/
.1..5.... 3.8...25. .....3.7. ..1.924.6 ....6.... 9.643.8.. .5.1..... .34...5.1 ....2..8. 712958643 348716259 695243178 571892436 483561792 926437815 259184367 834679521 167325984