#include <iostream>
#include <algorithm>
using namespace std;
int N,size,heap[100200];
int main()
{
scanf("%d",&N);
for(int x=0; x<N; x++)
{
int a;
scanf("%d",&a);
if(a>0)
{
heap[size++]=a;
push_heap(heap,heap+size);
}
else if(a==0)
{
if(size<1) printf("0\n");
else
{
printf("%d\n",heap[0]);
pop_heap(heap,heap+size);
size--;
}
}
}
}