#include <iostream>
#include <stack>

using namespace std;

int main() {
	int n;
	stack<int> s;
	while (true) {
		cin >> n;

		if (n == 0) {
			cout << s.top() << endl;
			s.pop();
		}
		else {
			s.push(n);
		}
	}
	return 0;
}