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;

}