// Get number of digits
    // in given number
    int len = num.Length;

    // Base cases
    if (len == 0)
    {
        Console.WriteLine("empty string");
        return;
    }
    if (len > 4)
    {
        Console.WriteLine("Length more than " +
                          "4 is not supported");
        return;
    }

    /* The first string is not used,
       it is to make array indexing simple */
    string[] single_digits = new string[]{ "zero", "one", "two",
                                           "three", "four", "five",
                                           "six", "seven", "eight",
                                           "nine"};

    /* The first string is not used,
       it is to make array indexing simple */
    string[] two_digits = new string[]{"", "ten", "eleven", "twelve",
                                       "thirteen", "fourteen",
                                       "fifteen", "sixteen", "seventeen",
                                       "eighteen", "nineteen"};

    /* The first two string are not used,
       they are to make array indexing simple*/
    string[] tens_multiple = new string[]{"", "", "twenty", "thirty",
                                          "forty", "fifty","sixty",
                                          "seventy", "eighty", "ninety"};

    string[] tens_power = new string[] {"hundred", "thousand"};

    /* Used for debugging purpose only */
    Console.Write((new string(num)) + ": ");

    /* For single digit number */
    if (len == 1)
    {
        Console.WriteLine(single_digits[num[0] - '0']);
        return;
    }

    /* Iterate while num
        is not '\0' */
    int x = 0;
    while (x < num.Length)
    {

        /* Code path for first 2 digits */
        if (len >= 3)
        {
            if (num[x]-'0' != 0)
            {
                Console.Write(single_digits[num[x] - '0'] + " ");
                Console.Write(tens_power[len - 3] + " ");

                // here len can be 3 or 4
            }
            --len;
        }

        /* Code path for last 2 digits */
        else
        {
            /* Need to explicitly handle
            10-19. Sum of the two digits
            is used as index of "two_digits"
            array of strings */
            if (num[x] - '0' == 1)
            {
                int sum = num[x] - '0' +
                          num[x] - '0';
                Console.WriteLine(two_digits[sum]);
                return;
            }

            /* Need to explicitely handle 20 */
            else if (num[x] - '0' == 2 &&
                     num[x + 1] - '0' == 0)
            {
                Console.WriteLine("twenty");
                return;
            }

            /* Rest of the two digit
            numbers i.e., 21 to 99 */
            else
            {
                int i = (num[x] - '0');
                if(i > 0)
                Console.Write(tens_multiple[i] + " ");
                else
                Console.Write("");
                ++x;
                if (num[x] - '0' != 0)
                    Console.WriteLine(single_digits[num[x] - '0']);
            }
        }
        ++x;