手打真累

#include <bits/stdc++.h>
using namespace std;
int main(){
    stack<int> st;
    int q; cin >> q;
    while(q--){
        string way; cin >> way;
        if(way == "empty" && st.empty()) cout << "yes\n";
        else if(way == "empty" && !st.empty()) cout << "no\n";
        else if(way == "push"){
            int n; cin >> n;
            st.push(n);
        }else if(way == "pop" && st.empty()) cout << "pop fail\n";
        else if(way == "pop" && !st.empty()){
            cout << "pop " << st.top() << endl;
            st.pop();
        }else if(way == "top" && st.empty()) cout << "top fail\n";
        else if(way == "top" && !st.empty()) cout << "top = " << st.top() << endl;
        else cout << "size = " << st.size() << endl;
    }
    return 0;
}