ref: a07a2025dab770421992362d8f4e4acbbf776fa8
dir: /sys/games/lib/sudoku/boards/easy-2005-03-08.su/
.425....6 9.17...5. .5...4.31 ....2.5.. ...3.1... ..3.7.... 73.1...6. .6...73.9 1....524. 342519786 981763452 657284931 416928573 879351624 523476198 734192865 265847319 198635247