ref: 05f721e9987791aae8e07dd4435f04df6ce33c77
dir: /sys/games/lib/sudoku/boards/medium-2005-01-24.su/
..6...7.. .2.5..4.6 4.93...2. 167..8... ....4.... ...2..519 .4...91.3 7.3..2.8. ..8...2.. 536824791 821597436 479361825 167958342 295143678 384276519 642789153 753612984 918435267