#include <iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    if (n < 10) {
        cout << "A\n";
    } else if (n < 20) {
        cout << "B\n";
    } else if (n < 40) {
        cout << "C\n";
    } else if (n < 50) {
        cout << "D\n";
    } else {
        cout << "E\n";
    }
    return 0;
}
/**************************************************************
	Problem: 1044
	User: 15159808820
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/