private void button4_Click(object sender, EventArgs e)
        {
            int number = Convert.ToInt32(this.textBox5.Text);
            //string output =  NumberToWords.ConvertNumberToStringByRecursion(number,"");
            string output = NumberToWords.ConvertNumberToStringByRecursionMethod2(number, new StringBuilder(), 0);

            this.textBox9.Text = output;
        }