ref: ed3a576e8b103032b659febc5d3c62565c9cf7d7
dir: /sys/games/lib/sudoku/boards/medium-2005-04-18.su/
6........ ..854.3.7 ..1.9..4. ...15..6. ..57.81.. .4..39... .5..1.8.. 9.3.675.. ........9 634871952 298546317 571392648 829154763 365728194 147639285 452913876 983467521 716285439