= 1 2 1 -1  0
+ 0 1       2
* 2 0       1
- 0         2
* 2 0       1
= -1 1 0 0  3
= 1 -1 0 0  4
* 3 4       5
- 5         5
* 5 5       5
* 5 5       5
* 5 5       5
Q