My code got WA for #27. After checking forever for errors, I edited my comparison for my set so that if two distances are equal, the distance with the bigger key will come first as a last desperation. After submitting this, I got AC.
I think this should be stated in the problem statement, because it affects the solutions.
For those that don't understand what I'm talking about:

Input:
2
1 1
1 1
1
1
(Before) WA 27
Output:
1
(After) AC
Output:
2

Your sample is incorrect. Because in the statment:
"The segments are ordered by non-decreasing ai, and when ai = aj they are ordered by decreasing length. All segments are distinct."