#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: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:26 ms
	Memory:2072 kb
****************************************************************/