public class acm2004 {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
while (in.hasNextInt()) {
int t = in.nextInt();
if (t < 0 || t > 100) {
System.out.println("Score is error!");
} else if (t < 60) {
System.out.println("E");
} else if (t < 70) {
System.out.println("D");
} else if (t < 80) {
System.out.println("C");
} else if (t < 90) {
System.out.println("B");
} else {
System.out.println("A");
}
}
}
}
