백준 자바 9498

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	int A = sc.nextInt();
	
	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");
	}
	
	}

}