Any idea where my code might be going wrong. I seem to not be able to see it.

My strategy is, use upper_bound for all the given starting and ending points of the contests to find out the shortest possible duration of stay for each contest. Time complexity is O(nlogn).

#include <bits/stdc++.h>
#include <algorithm>
#include <climits>
#include <cmath>
#include <deque>
#include <iostream>
#include <map>
#include <set>
#include <string>
#include <vector>