include <stdio.h>

int main() {

int s;
scanf("%d", &s);
if (90 <= s&&s <=100) {
	printf("A");
}
if (80 <= s&&s < 90) {
	printf("B");
}
if (70 <= s&&s < 80) {
	printf("C" );
}
if (60 <= s&&s < 70) {
	printf("D");
}
if (0 <= s&&s < 60) {
	printf("E");
}
return 0;

}