ref: f6d2a34de1a023671cae5ac6ec4a9c042e4bc34b
dir: /sys/games/lib/sudoku/boards/medium-2005-04-27.su/
.5...61.. .243..... 1......67 36...9... ..1...2.. ...5...76 47......9 .....458. ..51...4. 753986124 624371895 189452367 367829451 591647238 842513976 478235619 216794583 935168742