A = [
0  0  0   1   3    5  0   9 
0  3  6  -6  -6  -12  0   1 
0  2  4  -5  -7   14  0   1 
0  1  2   1  14   21  0  -1 
0  0  0   2   4    9  0   7 
0  5 10 -11 -13    2  0   2] 

