백준 #9498번 시험 성적

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