using System;

public class Program

{

    public static void Main()

    {

        int mark;

        char grade;

        Console.WriteLine("Please insert your grade");

        mark=Convert.ToInt32(Console.ReadLine());

        if(mark>=75 && mark<=100)

            Console.WriteLine('A');

        else if(mark>=50 && mark<=74)

            Console.WriteLine('B');

        else if(mark>=0 && mark>=49)

            Console.WriteLine('C');

    }

}