x x x x 1 x x 3 x
x x x 3 x 5 x x x
3 x x 7 x x 8 1 x

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

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