8
 0  1  0  0  0  0  0  0 
-1  0 -1  0  0  0  0  1
 0  1  0  1  0  1  0 -2
 0  0 -1  0 -1  0  0  1
 0  0  0  1  0  0  0  0
 0  0 -1  0  0  0 -1  1
 0  0  0  0  0  1  0  0
 0 -1  2 -1  0 -1  0  0