include <stdio.h>

int main () {

int s;
scanf("%d",&s);
if(90<=s&&100>=s){
    printf("A");
}
 if(80<=s&&90>s){
    printf("B");
}
 if(70<=s&&80>s){
    printf("C");
}
 if(60<=s&&70>s){
    printf("D");
}
 if(0<=s&&60>s){
    printf("E");
}
return 0;

}