include

using namespace std;

int main() {

int s ;
cin >> s;// 90  <= s <=100 
if (90 <= s && s <= 100)
	cout << 'A';
else if (80 <= s && s < 90)
	cout << 'B';
else if (70 <= s && s < 80)
	cout << 'C';
else if (60 <= s && s < 70)
	cout << 'D';
else
	cout << 'E';
return 0;

}