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

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

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