ref: 36c9a2489d1f0e3d4e6a890bb86edde64d719acb
dir: /sys/games/lib/sudoku/boards/medium-2005-03-24.su/
..3729.6. .2.8..73. ......... ..8..75.6 ..5...1.. 7.69..2.. ......... .74..5.9. .6.1784.. 543729861 921846735 687531924 298317546 435682179 716954283 852493617 174265398 369178452