#include <bits/stdc++.h>
using namespace std;

const int N=1e5+5;
int que[N];
int front=0;
int gear=-1;
int m;

int main(){
    memset(que, 0x00, sizeof que);
    cin>>m;
    string P;
    int x;
    while(m--){
        cin>>P;
        if(P=="push"){
            cin>>x;
            que[++gear]=x;
        }
        else if(P=="pop"){
            ++front;
        }
        else if(P=="empty"){
            cout<<(front>gear?"YES":"NO")<<endl;
        }
        else if(P=="query"){
            cout<<que[front]<<endl;
        }
    }

    return 0;
}