#include<bits/stdc++.h>
using namespace std;
int main() {
    int t;
    while(cin >> t) {
        if(t < 0 || t > 100) {
            cout << "Score is error!";
        } else if(t >= 90) {
            cout << "A";
        } else if(t >= 80) {
            cout << "B";
        } else if(t >= 70) {
            cout << "C";
        } else if(t >= 60) {
            cout << "D";
        } else {
            cout << "E";
        }
        cout << endl;
    }
    return 0;
}