NumbersToText

using System;

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

        if (number >= 0 && number <= 19)
        {
            switch (number)
            {
                case 0: Console.WriteLine("zero"); break;
                case 1: Console.WriteLine("one"); break;
                case 2: Console.WriteLine("two"); break;
                case 3: Console.WriteLine("three"); break;
                case 4: Console.WriteLine("four"); break;
                case 5: Console.WriteLine("five"); break;
                case 6: Console.WriteLine("six"); break;
                case 7: Console.WriteLine("seven"); break;
                case 8: Console.WriteLine("eight"); break;
                case 9: Console.WriteLine("nine"); break;
                case 10: Console.WriteLine("ten"); break;
                case 11: Console.WriteLine("eleven"); break;
                case 12: Console.WriteLine("twelve"); break;
                case 13: Console.WriteLine("thirteen"); break;
                case 14: Console.WriteLine("fourteen"); break;
                case 15: Console.WriteLine("fifteen"); break;
                case 16: Console.WriteLine("sixteen"); break;
                case 17: Console.WriteLine("seventeen"); break;
                case 18: Console.WriteLine("eighteen"); break;
                case 19: Console.WriteLine("nineteen"); break;
            }
        }
        else if (number >= 20 && number <= 99)
        {
            int tenths = number / 10;
            int units = number % 10;

            switch (tenths)
            {
                case 2: Console.Write("twenty"); break;
                case 3: Console.Write("thirty"); break;
                case 4: Console.Write("fourty"); break;
                case 5: Console.Write("fifty"); break;
                case 6: Console.Write("sixty"); break;
                case 7: Console.Write("seventy"); break;
                case 8: Console.Write("eighty"); break;
                case 9: Console.Write("ninety"); break;
            }

            switch (units)
            {
                case 1: Console.WriteLine(" one"); break;
                case 2: Console.WriteLine(" two"); break;
                case 3: Console.WriteLine(" three"); break;
                case 4: Console.WriteLine(" four"); break;
                case 5: Console.WriteLine(" five"); break;
                case 6: Console.WriteLine(" six"); break;
                case 7: Console.WriteLine(" seven"); break;
                case 8: Console.WriteLine(" eight"); break;
                case 9: Console.WriteLine(" nine"); break;
            }
        }
        else if (number == 100)
        {
            Console.WriteLine("one hundred");
        }
        else
        {
            Console.WriteLine("invalid number");
        }
    }
}