#include <iostream>

int main() {
    int score;
    std::cin >> score;

    char grade;
    if (score >= 90) {
        grade = 'A';
    } else if (score >= 80) {
        grade = 'B';
    } else if (score >= 70) {
        grade = 'C';
    } else if (score >= 60) {
        grade = 'D';
    } else {
        grade = 'E';
    }

    std::cout << grade << std::endl;

    return 0;
}