#include<iostream>
#include<string> 

using namespace std;

const int N = 1e5 + 10;
int q[N];
int tail,head;

void init()     //初始化
{
    head = -1;
    tail = -1;
}

void push(int x)
{
    q[++tail] = x;
}

void pop()
{
    head++;
}

void empty()
{
    if(head < tail) cout<<"NO"<<endl;
    else cout<<"YES"<<endl;
}

void query()
{
    cout<<q[head + 1]<<endl;
}

int main()
{
    init();
    int m;
    string s;
    cin>>m;
    while(m--)
    {
        cin>>s;
        if(s == "push")
        {
            int x;
            cin>>x;
            push(x);
        }
        else if(s == "pop") pop();
        else if(s == "empty") empty();
        else query();
    }

    return 0;
}