#include <iostream>
#include <vector>

int main(){

    std::vector<int> vehicle_order;
    int input_data;

    while(std::cin >> input_data){
        if(input_data == 0){
            std::cout << vehicle_order.back() << std::endl;
            vehicle_order.pop_back();
        }else{
            vehicle_order.push_back(input_data);
        }
    }

    return 0;
}