#include <stdio.h>
int main(void){
int score;
char grade;
scanf("%d",&score);
if(score<0 && score>100){
printf("Error Input!");
}
switch(score/10){
case 10:
case 9:
grade = 'A';
printf("%c",grade);
break;
case 8:
grade = 'B';
printf("%c",grade);
break;
case 7:
grade = 'C';
printf("%c",grade);
break;
case 6:
grade = 'D';
printf("%c",grade);
break;
default:
grade = 'E';
printf("%c",grade);
}
return 0;
}