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