#include <iostream>
#include <iomanip>
using namespace std;
int main(){
    int a;
    while(cin>>a){
        if(a>100 || a<0)
            cout << "Score is error!" << endl;
        else if (a > 89)
            cout <<  "A"<<endl;
        else if (a > 79)
            cout << "B" << endl;
        else if (a > 69)
            cout << "C" << endl;
        else if (a > 59)
            cout << "D" << endl;
        else
            cout << "E" << endl;
    }
    return 0;
}