int main()
{
int m;
while(scanf("%d",&m)!=EOF)
{
if(m>=90&&m<=100) printf("A\n");
else if(m>=80&&m<=89) printf("B\n");
else if(m>=70&&m<=79) printf("C\n");
else if(m>=60&&m<=69) printf("D\n");
else if(m>=0&&m<=59) printf("E\n");
else printf("Score is error!\n");
}
return 0;
}