Problem:
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Priority Queue

A priority queue is a data structure which maintains a set $S$ of elements, each of with an associated value (key), and supports the following operations:

$insert(S, k)$: insert an element $k$ into the set $S$

$extractMax(S)$: remove and return the element of $S$ with the largest key

Write a program which performs the $insert(S, k)$ and $extractMax(S)$ operations to a priority queue $S$.
The priority queue manages a set of integers, which are also keys for the priority.

Input

Multiple operations to the priority queue $S$ are given. Each operation is given by "insert $k$", "extract" or "end" in a line. Here, $k$ represents an integer element to be inserted to the priority queue.

The input ends with "end" operation.

Output

For each "extract" operation, print the element extracted from the priority queue $S$ in a line.

Constraints

The number of operations $\leq 2,000,000$

$0 \leq k \leq 2,000,000,000$

Sample Input 1

insert 8
insert 2
extract
insert 10
extract
insert 11
extract
extract
end

Sample Output 1

8
10
11
2

Solution in C++14 (judge verdict: Accepted)

#include <bits/stdc++.h>

#define REP(i, n) for(int i = 0; i < n; i++)
using namespace std;

int main()
{   
    string s;
    int num;
    priority_queue<int> Q;

    while (cin >> s && s != "end") {
        
        if (s == "insert") {
            cin >> num;
            Q.push(num);
        }

        else if (s == "extract") {
            cout << Q.top() << endl;
            Q.pop();
        }
    }
}