I apparently entered my test cases wrong in lots of interesting ways. I think I've actually found essentially the same solution you have, it turns out I had th

I apparently entered my test cases wrong in lots of interesting ways. I think I've actually found essentially the same solution you have, it turns out I had the exceptions and the actual solution backwards: n avargl qrterr ebgngvba naq n ersyrpgvba nobhg, nf sne nf V pna gryy nal, yvar guebhtu gur bevtva frrzf gb tvir gur evtug erfhyg. Are we sure this is the correct meaning for "A = -B", where A and B are matrices? Some things I've read seem to be saying that that should be equivalent to AB = identity matrix, rather than Av = -1(Bv), where v is some vector.