c

1

0 4

0

1

6 7 1 0 2 2
1     0    -5     0     0     1     0
1     0     5     0     0    -1     2
1     0     0   -11     1     0     0
1     0     0    11    -1     0     6
1     1     0     0     0     0     0
1    -1     0     0     1     1     0

0 0 0

0

0