#include <iostream>
#include <string>
#include <map>
#include <vector>
#include <algorithm>
#include <stdio.h>
#include <math.h>
#include <iomanip>
#include <stack>
using namespace std;
int main(){
  int n;
  stack<int> in,out;
  while(cin>>n){
    if(!n)out.push(in.top()),in.pop(),cout<<out.top()<<endl;
    else{in.push(n);}
    if(in.empty()&&!out.empty())return 0;
  }
}