#include<stdio.h>
main(){
int a;
while(scanf("%d",&a)!=EOF)
{
if(a<0||a>100) printf("Score is error!\n");
else if(a>=90) printf("A\n");
else if(a>=80) printf("B\n");
else if(a>=70) printf("C\n");
else if(a>=60) printf("D\n");
else if(a<60) printf("E\n");
}
}