//
//	P.36 #1
//

import java.util.Scanner;

class ToLetter
{
	public static void main(String[] args)
	{
		Scanner input = new Scanner(System.in);

		System.out.print("Score? ");
		double score = input.nextDouble();
		char letter = 'F';

		if(score>=89.5)	letter = 'A';
		else if(score >= 79.5) letter = 'B';
		else if(score >= 69.5) letter = 'C';
		else if(score >= 59.5) letter = 'D';

		System.out.println("Letter = " + letter);

		System.out.println("\n\nDone.\n\n\n");
	}
}