ref: 5f7a6b7ea3c4ae1b51beffe3309e9b6b0491e71f
dir: /sys/games/lib/sudoku/boards/medium-2005-02-21.su/
.....94.. ...2.8..7 47..1.3.. 5.9..6..2 ..8...1.. 3..5..8.9 ..5.9..81 8..3.2... ..48..... 186739425 953248617 472615398 549186732 768923154 321574869 635497281 817352946 294861573