#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;
    cin>>n;
    if(n<10) cout<<"A"<<endl;
    else if(n>=10&&n<20) cout<<"B"<<endl;
    else if(n>=20&&n<40) cout<<"C"<<endl;
    else if(n>=40&&n<50) cout<<"D"<<endl;
    else if(n>=50&&n<80) cout<<"E"<<endl;
    }
/**************************************************************
	Problem: 1044
	User: wangchenyu
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/