using System;

public class Program

{

    public static void Main()

    {

        // PROGRAM OF IF

        // וגם if ((grade >= 80) && (grade <= 89))

        //   if ((day == "friday") || (day == "saturday"))  או

         Console.WriteLine("ENTER A NUM");

        string gradeString = Console.ReadLine();

int grade = Convert.ToInt32(gradeString);

if ((grade >= 90) && (grade <= 100))

{

    Console.WriteLine("VERY GOOD");

}

else if ((grade >= 80) && (grade <= 89))

{

    Console.WriteLine("GOOD");

}

else if ((grade >= 70) && (grade <= 79))

{

    Console.WriteLine("NOT GOOD");

}

else if ((grade >= 60) && (grade <= 69))

{

    Console.WriteLine("BAD");

}

else

{

    Console.WriteLine("F");

}

    }

}