#include<stdio.h>
#include<stack>

int main(){
	int data[100]={0},i=0;
	std::stack<int> train;
	while(data[i] != EOF){
		scanf("%d",&data[i]);
		i++;
	}
	i=0;
	train.push(data[i]);
	i=1;
	while(1){
		if(! train.empty()){
			if(data[i]==0){
				printf("%d\n",train.top());
				train.pop();
			}else{
				train.push(data[i]);
			}
		i++;
		}else{
			break;
		}
	}
	return 0;
}