[백준] 9498번

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int A = sc.nextInt();
        sc.close();

        if (A >= 90) System.out.println('A');
        else if (A >=80) System.out.println('B');
        else if (A >=70) System.out.println('C');
        else if (A >=60) System.out.println('D');
        else System.out.println('F');
        }
}