#include<bits/stdc++.h>
using namespace std;
int main()
{
	long long a;
	cin>>a;
	if(a>89)
	{
		cout<<"A";
	}else if(a>79)
	{
		cout<<"B";
	}else if(a>69)
	{
		cout<<"C";
	}else if(a>59)
	{
		cout<<"D";
	}else
	{
		cout<<"E";
	}
	
	return 0;
}