#include "bits/stdc++.h"
using namespace std;

long long int gcd(long long int l, long long int r) {
	assert(l > 0 && r > 0);
	if (l > r)return gcd(r, l);
	else {
		const long long int num = r%l;
		if (num) {
			return gcd(l, num);
		}
		else {
			return l;
		}
	}
}
long long int lca(long long int l, long long int r) {
	return l / gcd(l, r)*r;
}
int getans(const int num, const int rest) {
	if (rest) {
		int ans = 0;
		for (int i = 0; i <= 9; ++i) {
			if (num >= i) {
				ans += getans(num - i, rest - 1);
			}
		}
		return ans;
	}
	else {
		return num == 0;
	}
}
int main() {
	int N;
	stack<int>sta;
	while (cin >> N) {
		
		if (N) {
			sta.emplace(N);
		}
		else {
			cout << sta.top() << endl;
			sta.pop();
		}
	}
	return 0;
}