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

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

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