#include <iostream>
#include <vector>

using namespace std;

int main()
{
	int n;
	vector<int> train;
	while (cin >> n) {
		if (n) {
			train.push_back(n);
		}
		else {
			cout << train.back() << endl;
			train.pop_back();
		}
	}
	return 0;
}