ref: ce1edc34368d192db7d3421673ca98c19cc792b2
dir: /sys/games/lib/sudoku/boards/hard-2005-05-21.su/
.3...5..2 ..2.6..8. .9......7 ..9.765.. .5.9.8.1. ..154.6.. 9......4. .6..8.2.. 7..3...9. 437895162 512764983 698213457 349176528 256938714 871542639 985627341 163489275 724351896