using LL  = long long;
using PLI = pair<LL,int>;
class Solution {
public:
    int mostBooked(int n, vector<vector<int>>& meetings) 
    {
        priority_queue<PLI, vector<PLI>, greater<>>busy;
        priority_queue<int, vector<int>, greater<>>free;
        for (int i=0; i<n; i++)        
            free.push(i);


        sort(meetings.begin(), meetings.end());                
        vector<LL>count(n);        

        for (int i=0; i<meetings.size(); i++)            
        {
            LL start = meetings[i][0];
            LL end = meetings[i][1];

            while (!busy.empty() && busy.top().first <= start)
            {
                free.push(busy.top().second);
                busy.pop();
            }

            if (!free.empty())
            {
                int idx = free.top();
                count[idx]++;                
                free.pop();
                busy.push({end, idx});                                
            }
            else
            {
                auto [time, idx] = busy.top();
                count[idx] += 1;
                busy.pop();
                busy.push({time + end- start, idx});                
            }

        }

        return max_element(count.begin(), count.end()) - count.begin();
    }
};