x x x  x 6 x  x 7 x
7 x x  x x 8  x x x
x x 3  1 x x  x x 8

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

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