题目链接：模拟栈

#include <iostream>

using namespace std;

const int N = 100010;

int m;
int stk[N], tt;

int main()
{
    cin >> m;
    while(m--)
    {
        string op;
        int x;
        cin >> op;
        if(op == "push") 
        {
            cin >> x;
            stk[++tt] = x;
        }
        else if(op == "pop") tt--;
        else if(op == "empty") cout << (tt ? "NO":"YES") <<endl;
        else cout << stk[tt] <<endl;
    }
    return 0;
}