why?

I have passed through it by changing the place where I considered that a particular stripe has been already rotated. I have no idea why it was wrong though.

I got WA 27, and I found that my program could not pass the following test:

7 2
6 4
5 3

The correct answer should be 1 -2 or 2 -1, but my incorrect program output 0. I fixed it and got AC.