using System;

public class Program

{

    public static void Main()

    {

        string input;

        int number;

        bool isValid;

        bool isUK = false;

        Console.WriteLine("\nEnter '0' to quit the program at any time\n");

        while (true)

             {

            Console.Write("Enter number: ");

            input = Console.ReadLine();

            isValid = int.TryParse(input, out number);

            if (!isValid)

                Console.WriteLine("\n  Not an integer, please try again\n");

            else

                Console.WriteLine("\n  {0}\n", NumberToText(number, isUK));

        }

        while (!(isValid && number == 0));

        Console.WriteLine("\nProgram ended");

    }

 public static string NumberToText(int number, bool isUK)

    {

        if (number == 0) return "Zero";

        string and = isUK ? "and " : ""; // deals with UK or US numbering

        if (number == -2147483648) return "Minus Two Billion One Hundred " + and +

        "Forty Seven Million Four Hundred " + and + "Eighty Three Thousand " +

        "Six Hundred " + and + "Forty Eight";

        int[] num = new int[4];

        int first = 0;

        int u, h, t;

        System.Text.StringBuilder sb = new System.Text.StringBuilder(); 

        if (number < 0)

        {

            sb.Append("Minus ");

            number = -number;

        }

             string[] words0 = {"", "One ", "Two ", "Three ", "Four ", "Five ", "Six ", "Seven ", "Eight ", "Nine "};

        string[] words1 = {"Ten ", "Eleven ", "Twelve ", "Thirteen ", "Fourteen ", "Fifteen ", "Sixteen ", "Seventeen ", "Eighteen ", "Nineteen "};

        string[] words2 = {"Twenty ", "Thirty ", "Forty ", "Fifty ", "Sixty ", "Seventy ", "Eighty ", "Ninety "};

        string[] words3 = { "Thousand ", "Million ", "Billion " };

        num[0] = number % 1000;           // units

        num[1] = number / 1000;

        num[2] = number / 1000000;

        num[1] = num[1] - 1000 * num[2];  // thousands

        num[3] = number / 1000000000;     // billions

        num[2] = num[2] - 1000 * num[3];  // millions

        for (int i = 3; i > 0; i--)

        {

            if (num[i] != 0)

            {

                first = i;

                break;

            }

        }

        for (int i = first; i >= 0; i--)

     {

            if (num[i] == 0) continue;

            u = num[i] % 10;              // ones

            t = num[i] / 10;

            h = num[i] / 100;             // hundreds

            t = t - 10 * h;               // tens

            if (h > 0) sb.Append(words0[h] + "Hundred ");

            if (u > 0 || t > 0)

            {

                if (h > 0 || i < first) sb.Append(and);

                if (t == 0)

                    sb.Append(words0[u]);

                else if (t == 1)

                    sb.Append(words1[u]);

                else

                    sb.Append(words2[t - 2] + words0[u]);

            }

            if (i != 0) sb.Append(words3[i - 1]);

        }

        return sb.ToString().TrimEnd();

    }

}