include <bits/stdc++.h>

using namespace std;

int main() {

int s;
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;

}