include

using namespace std; int s, A, B, C, D, E;

int main() {

cin >> s;
if (90 <= s && s <= 100) {
	cout << "A";
}
if (80 <= s && s < 90) {
	cout << "B";
}
if (70 <= s && s < 80) {
	cout << "C";
}
if (60 <= s && s < 70) {
	cout << "D";
}
if (0 <= s && s < 60) {

	cout << "E";
}

return 0;

}