using System;

public class Program

{

    public static void Main()

    {

        // 1. You cannot use double types in a Switch statement because we can only differentiate double values to a certain precision.  At some point, different values have the same bit combo.

        // 2. No, we cannot have duplicate cases in a Switch.

        // 3. No, variables cannot be used in cases.

        // 4.

        Console.WriteLine("Enter your major.");

        string Major = Console.ReadLine();

        Console.WriteLine("Enter your score.");

        int intScore;

        string Grade;

        string strScore = Console.ReadLine();

        bool IsValidNumber = Int32.TryParse(strScore, out intScore);

            if (IsValidNumber == false)

            {

            Console.WriteLine("You did not enter a whole number.");

                return;

            }

            if (intScore < 0 || intScore > 100)

            {

                Console.WriteLine("Score is not in range.");

                return;

            }

            if (intScore >= 90)

            {

                Grade = "A";

            }

            else if (intScore >= 80)

            {

                Grade = "B";

            }

            else if (intScore >= 70)

            {

                Grade = "C";

            }

            else if (intScore >= 60)

            {

                Grade = "D";

            }

            else

            {

                Grade = "F";

            }

        Console.WriteLine("You get " + Grade + ".");    

            if (intScore > 90)

            {

                if (Major == "IS")

                {

                    Console.WriteLine("Congratulations! You are one of the best students in " + Major + ".");

                }

                else

                {

                    Console.WriteLine("Congratulations! You are one of the best students.");

                }

            }

    }

}