#include <iostream>
#include <stack>
using namespace std;

int main(void)
{
    stack<int> s;
    int n;
    while (cin >> n) {
        if (n == 0) {
            cout << s.top() << endl;
            s.pop();
        }
        else
            s.push(n);
    }
    return 0;
}




