8

1 0 1 0 1 1 0 1

0 1 0 1 1 1 0 1

1 0 1 0 1 1 0 1

0 1 0 1 1 0 0 1

1 0 1 0 1 1 0 1
1 0 1 0 1 1 0 1

0 1 1 1 1 0 0 0

1 0 1 0 1 1 0 1