ref: c2a5d7e3f28e86aeef1e4e37e2b88e46af90b62c
dir: /sys/games/lib/sudoku/boards/hard-2005-04-09.su/
..58.4.2. .....5..9 .1....5.3 ...39.8.. 2.8...7.1 ..9.81... 5.4....1. 7..6..... .8.5.39.. 965834127 347125689 812967543 471392865 238456791 659781234 594278316 723619458 186543972