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

/**************************************************************
	Problem: 1044
	User: lzc
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/