include <stdio.h>

int main() {

int s;
scanf("%d", &s);
if (90 <= s && s <= 100) {
	printf("A");
}

else if (80 <= s && s <= 90) {
	printf("B");
}

else if (70 <= s && s <= 80) {
	printf("C");
}

else if (60 <= s && s <= 70) {
	printf("D");
}

else if (0 <= s && s <= 60) {
	printf("E");
}

return 0;

}