#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);
		}
	}
	while(1);
	return 0;
}
	