#include<iostream>
using namespace std;
int main()
{
	int x;
	cin >> x;
	if (x >= 90 && x <= 100)
		cout << "A" << endl;
	else if (x >= 80 && x < 90)
		cout << "B" << endl;
	else if (x >= 70 && x < 80)
		cout << "C" << endl;
	else if (x >= 60 && x < 70)
		cout << "D" << endl;
	else if (x >= 0 && x < 60)
		cout << "E" << endl;
	else
		exit(1);
	return 0;
}