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