I experienced a strange WA on 576C - Точки на плоскости.

Compare these two submissions: 13000332 and 13000388. They are exactly the same, except that one submission had comparators <= and >=, while the other had comparators < and >. There shouldn't be any undefined behaviour as far as I can see, so I'm wondering why the WA in the first submission.

This would have been very frustrating had it been during a contest... Is there anything I'm missing here?