Test

namespace _1000DaysAfterBirth
{
    using System;
    using System.Collections.Generic;
    using System.Globalization;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;

    public class Program
    {
        public static void Main()
        {
            int numberInput = int.Parse(Console.ReadLine());

            string[] firstNineteenNumbers = new string[]
            {
                "Zero",
                "One",
                "Two",
                "Three",
                "Four",
                "Five",
                "Six",
                "Seven",
                "Eight",
                "Nine",
                "Ten",
                "Eleven",
                "Twelve",
                "Thirteen",
                "Fourteen",
                "Fifteen",
                "Sixteen",
                "Seventeen",
                "Eighteen",
                "Nineteen"
            };

            string result = string.Empty;
            if (numberInput >= 0 && numberInput <= 19)
            {
                result = firstNineteenNumbers[numberInput];
            }
            else if (numberInput >= 20 && numberInput < 100)
            {
                string[] tens = new string[] { "Twenty ", "Thirty ", "Forty ", "Fifty ", "Sixty ", "Seventy ", "Eighty ", "Ninety " };

                string secondNumber = numberInput % 10 == 0 ? string.Empty : firstNineteenNumbers[numberInput % 10];

                result = (tens[numberInput / 10 - 2] + secondNumber);
            }
            else if (numberInput == 100)
            {
                result = "one hundred";
            }

            Console.WriteLine(result.TrimEnd());
        }
    }
}