include

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;

}