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

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

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