Number as Words

using System;

class Program
{
    public static string DigitAsWord(int number)
    {
        string str = "";
        switch (number)
        {
            case 0: str = ""; break;
            case 1: str = "One"; break;
            case 2: str = "Two"; break;
            case 3: str = "Three"; break;
            case 4: str = "Four"; break;
            case 5: str = "Five"; break;
            case 6: str = "Six"; break;
            case 7: str = "Seven"; break;
            case 8: str = "Eight"; break;
            case 9: str = "Nine"; break;
            case 10: str = "ten"; break;
            case 11: str = "eleven"; break;
            case 12: str = "twelve"; break;
            case 13: str = "thirteen"; break;
            case 14: str = "fourteen"; break;
            case 15: str = "fifteen"; break;
            case 16: str = "sixteen"; break;
            case 17: str = "seventeen"; break;
            case 18: str = "eighteen"; break;
            case 19: str = "nineteen"; break;
            case 20: str = "twenty"; break;
            case 30: str = "thirty"; break;
            case 40: str = "forty"; break;
            case 50: str = "fifty"; break;

        }
        return str;

    }



    static void Main()
    {
        int number = int.Parse(Console.ReadLine());

        if (number >= 100)
        {
            if ((number % 100) <= 20)
            {
                Console.WriteLine(DigitAsWord(number / 100) + " hundred and " + DigitAsWord(number % 100));
            }

            if (number % 100 / 10 == 3 || number % 100 / 10 == 4 || number % 100 / 10 == 5 || number % 100 / 10 == 2)
            {
                Console.WriteLine(DigitAsWord(number / 100) + " hundred and " + DigitAsWord((number % 100) - (number % 10)) + " " + DigitAsWord(number % 10));
                return;

            }
            else if (number / 10 != 11)
            {
                Console.WriteLine(DigitAsWord(number / 100) + " hundred and " + DigitAsWord(((number % 100) - (number % 10)) / 10) + "ty " + DigitAsWord(number % 10));

            }
        }
        if (number < 100 && number > 20)
        {
            if (number >= 60)
            {
                Console.WriteLine(DigitAsWord(number / 10) + "ty" + " " + DigitAsWord(number % 10));
            }
            else
            {
                Console.WriteLine(DigitAsWord(number - (number % 10)) + " " + DigitAsWord(number % 10));
            }
        }
        if (number <= 20)
        {
            Console.WriteLine(DigitAsWord(number));
        }
    }
 }