https://www.acmicpc.net/problem/9498
import java.util.Scanner;
class Main {
static public void main(String[] args) {
Scanner sc = new Scanner(System.in);
int test = sc.nextInt();
if (100 >= test && 90 <= test)
System.out.println("A");
else if (89 >= test && 80 <= test)
System.out.println("B");
else if (79 >= test && 70 <= test)
System.out.println("C");
else if (69 >= test && 60 <= test)
System.out.println("D");
else
System.out.println("F");
sc.close();
}
}