#include<stdio.h>   

int main(){ 
	int a;
	
	scanf("%d",&a);
	
	if(a < 10){
		printf("A");
	}else if(a >= 10 && a < 20){
		printf("B");
	}else if(a >= 20 && a < 40){
		printf("C");
	}else if(a >= 40 && a < 50){
		printf("D");
	}else if(a >= 50 && a < 80){
		printf("E");
	}

	return 0;
} 
/**************************************************************
	Problem: 1044
	User: admin
	Language: C
	Result: Accepted
	Time:15 ms
	Memory:1144 kb
****************************************************************/