#include<iostream>
using namespace std;
int q[100005],t=-1;
int main()
{
    int m,h,x;
    scanf("%d",&m);
    while(m--){
        string op;
        cin>>op;
        if(op=="push"){
            scanf("%d",&x);
            t++,q[t]=x;
        }
        else if(op=="pop")h++;
        else if(op=="empty")printf((h<=t?"NO\n":"YES\n"));
        else printf("%d\n",q[h]);
    }
    return 0;
}