백준 1927 c++

#include <iostream>
#include <queue>
#include <climits>
#include <algorithm>

using namespace std;

int input(int lower, int upper)
{
	//cout << "input()" << endl;
	int A;

	while (1)
	{
		//scanf("%d", &A);
		cin >> A;
		if (A >= lower && A <= upper)
		{
			break;
		}
		else
		{
			;
		}
	}

	return A;
}

int main(void)
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);

	int N, i, x;
	priority_queue<int, vector<int>, greater<int>> min_heap;

	N = input(1, 100000);
	for (i = 0; i < N; i++)
	{
		x = input(0, INT_MAX);
		if (x == 0)
		{
			if (min_heap.size() == 0)
			{
				cout << "0\n";
			}
			else
			{
				cout << min_heap.top() << "\n";
				min_heap.pop();
			}
		}
		else
		{
			min_heap.push(x);
		}
	}

	return 0;
}