#include <iostream>
#include <string>

using namespace std;

const int N = 100010;

int q[N];
int head = 0, tail = -1;

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

void pop() {
    head++;
}

void empty() {
    if (tail >= head) puts("NO");
    else puts("YES");
}

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

int main(void)
{
    int m, x;
    cin >> m;

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

    return 0;
}