9498번 : 시험 성적

import java.io.IOException;
import java.util.Scanner;
 
public class Main {
 
    public static void main(String[] args) throws Exception, IOException {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        if (n>=90 && n<=100) {
            System.out.println("A");
        } else if (n >=80 && n<=89) {
            System.out.println("B");
        } else if (n >=70 && n<=79) {
            System.out.println("C");
        } else if (n >=60 && n<=69) {
            System.out.println("D");
        } else {
            System.out.println("F");
        }
    }
 
}