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;

}