#include <iostream>
#include <stack>
 
int main(){
    std::stack<u_int> train;
    u_int num;
    while(std::cin >> num){
        if(num == 0){
            std::cout << train.top() << std::endl;
            train.pop();
        }
        else {
            train.push(num);
        }
    }
    return 0;
}