x 7 x 5 x 4 x 2 x
x x x x x x 7 x x
6 x 4 x x x 1 x 9
x x x 3 x 9 x x x
x 9 2 x x x 5 8 x
x x x 2 x 5 x x x
4 x 1 x x x 6 x 8
x x 6 x x x x x x
x 3 x 8 x 6 x 9 x