4
 1 -1
 5  3  4 -8  0  0
15  0  0  3  0  0  4  0  0  -8  0  0  0  0  0  0
 0 4
 1 -1
 5  3  4 -8  0  0
15  0  0  3  0  0  4  0  0  -8  0  0  0  0  0  0
 0