10_ApplyBonusScores

using System;

class ApplyBonusScores
{
    static void Main()
    {
        int digit;

        Console.Write("Please enter а number into the range [1..9]: ");
        string str = Console.ReadLine();

        if (!int.TryParse(str, out digit))
        {
            Console.WriteLine("Invalid number: {0}", str);
        }
        else
        {
            while (digit <= 1 || digit >= 9)
            {
                Console.WriteLine("Please enter correct number!");
                string strSecond = Console.ReadLine();

                if (!int.TryParse(strSecond, out digit))
                {
                    Console.WriteLine("Invalid number: {0}", strSecond);
                }
            }

            switch (digit)
            {
                case 1:
                case 2:
                case 3:
                    digit *= 10;
                    break;

                case 4:
                case 5:
                case 6:
                    digit *= 100;
                    break;

                case 7:
                case 8:
                case 9:
                    digit *= 1000;
                    break;

                default:
                    Console.WriteLine("Wrong number entered!");
                    break;
            }

            Console.WriteLine("The new value is {0}.", digit);
        }
    }
}