#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm> 
#include<string>
#include<cstring>
using namespace std;
int main()
{
    int n;
    cin >> n;
    if (n >= 90)cout << 'A' << endl;
    else if (n >= 80) cout << 'B' << endl;
    else if (n >= 70) cout << 'C' << endl;
    else if (n >= 60) cout << 'D' << endl;
    else cout << 'E' << endl;
    return 0;
}