#include <iostream>
using namespace std;
const int N = 1e5 + 10;
int q[N], hh = 0, tt = -1;

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

void pop()
{
    hh++;
}

void empty()
{
    cout << (hh <= tt? "NO":"YES") << endl;
}

void query()
{
    cout << q[hh] << endl;
}
int main()
{
    int n, x;
    cin >> n;
    string opr;
    while(n --)
    {
        cin >> opr;
        if(opr == "push")
        {
            cin >> x;
            push(x);
        }
        else if(opr == "pop")
        {
            pop();
        }
        else if(opr == "empty")
        {
            empty();
        }
        else
        {
            query();
        }
    }

    return 0;
}