#include <iostream>
#include <stack>

using namespace std;

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

    return 0;
}