include[HTML_REMOVED]

using namespace std;
const int N=100010;
int stk[N],tt;
int m;
int main()
{
cin>>m;
while(m–)
{
int x;
string op;
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;

}