/* http://www.sudoku-knacker.de/ sehr schwer Feld 16017 */
1 7 0 0 0 0 0 4 2
0 0 0 0 0 7 0 0 0
0 0 6 5 0 0 0 1 9
0 0 0 8 0 5 0 0 4
0 0 2 0 0 0 3 0 0
7 0 0 4 0 1 0 0 0
6 5 0 0 0 2 4 0 0
0 0 0 9 0 0 0 0 0
8 3 0 0 0 0 0 9 6