Astrological Digits

using System;
class AstrologicalDigits
{
  static void Main()
  {
    //Telerik Academy
    //The astrological digit of a given number N is a digit calculated by the number's digits by a special algorithm. The algorithm performs the following steps:
    //(1)   Sums the digits of the number N and stores the result back in N.
    //(2)   If the obtained result is bigger than 9, step (1) is repeated, otherwise the algorithm finishes.
    //The last obtained value of N is the result, calculated by the algorithm.

    string numberInput = Console.ReadLine();
    int sum = 0;
    string buffer = numberInput;

    do
    {
      sum = 0;
      foreach (char item in buffer)
      {
        if (item != '.' && item != '-')
        {
          sum += (int)item - '0';

        }
      }
      if (sum <= 9)
      {
        break;
      }
      else
      {
        buffer = Convert.ToString(sum);
      }
    } while (sum > 9);

    Console.WriteLine(sum);
  }
}