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#define _CRT_SECURE_NO_DEPRECATE

#include <iostream>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>

#define li long long

using namespace std;

int main() {
	int n;
	cin >> n;
	multiset<int> a;
	for (int i = 0; i < n; i++) {
		int c;
		cin >> c;
		if (c == 0) {
			cout << *a.begin() << endl;
			a.erase(a.begin());
		}
		else {
			a.insert(c);
		}
	}

}