#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a;
    cin>>a;
    if(a<10) cout<<"A";
    else if(a<20) cout<<"B";
         else if(a<40) cout<<"C";
              else if(a<50) cout<<"D";
                   else if(a<80) cout<<"E";
	return 0;
}

/**************************************************************
	Problem: 1044
	User: ccf
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/