ref: 1f3c43c01720ed66e7c981d3287eca7dae362ba8
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