ref: c2a5d7e3f28e86aeef1e4e37e2b88e46af90b62c
dir: /sys/games/lib/sudoku/boards/medium-2005-04-01.su/
...74.8.. ....137.9 ..1...65. 4..9..... 31.....68 .....4..5 .54...2.. 6.735.... ..8.92... 593746812 286513749 741829653 465938127 319275468 872164395 954687231 627351984 138492576