#include<iostream>
 using namespace std;

int n;

int main()
{
	cin>>n;
	if(n<60)
		cout<<"E"<<endl;
	else if(n<=69)
		cout<<"D"<<endl;
	else if(n<=79)
		cout<<"C"<<endl;
	else if(n<=89)
		cout<<"B"<<endl;
	else
		cout<<"A"<<endl;
	return 0;
}