#include<bits/stdc++.h>
using namespace std;
   
int main(){
    int n;
    cin>>n;
    if(n<10){
        cout<<"A";
    }
    if(n>=10&&n<20){
        cout<<"B";
    }
    if(n>=20&&n<40){
        cout<<"C";
    }
    if(n>=40&&n<50){
        cout<<"D";
    }
    if(n>=50&&n<80){
        cout<<"E";
    }
}
/**************************************************************
	Problem: 1044
	User: wengzihang
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/