class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(IncreaseOne("1631.10.002"));
            Console.WriteLine(IncreaseOne("5465.5121.85.215"));
            Console.WriteLine(IncreaseOne("123"));
            Console.Read();
        }

        private static string IncreaseOne(String num)
        {
            string[] strs = num.Split('.');
            if (strs.Length > 1)
            {
                string temp = strs[strs.Length - 1];
                int len = temp.Length;
                int lastNum = Convert.ToInt32(temp) + 1;
                strs[strs.Length - 1] = lastNum.ToString().PadLeft(len, '0');
            }
            else
            {
                strs[strs.Length - 1] = (Convert.ToInt32(strs[strs.Length - 1]) + 1).ToString();
            }
            string result = string.Empty;
            foreach (string str in strs)
            {
                if (result.Length == 0)
                    result += str;
                else
                    result = result + ("." + str);
            }
            return result;
        }
    }