#include <iostream>
#include <stack>
using namespace std;
int main()
{
	stack<int>s;
	int n;
	while (cin >> n)
	{
		if (n!= 0)
		{
			s.push(n);
		}
		else
		{
			cout << s.top() << endl;
			s.pop();
		}
	}
};
