AstrologDigits

using System;

class AstrologDigits
{
    static void Main()
    {
        ulong astroSum = 0;
        while (true)
        {
            int chDigit = Console.Read();
            if (chDigit == (int)'\n' || chDigit == (int)'\r' || chDigit == -1)
            {
                break;
            }
            if (chDigit >= '0' && chDigit <= '9')
            {
                ulong digit = (ulong)chDigit - (ulong)'0';
                astroSum = astroSum + digit;
            }
        }

        while (astroSum > 9)
        {
            ulong tempAstroSum = 0;
            while (astroSum > 0)
            {
                ulong lastDigit = astroSum % 10;
                tempAstroSum = tempAstroSum + lastDigit;
                astroSum = astroSum / 10;
            }
            astroSum = tempAstroSum;
        }

        Console.WriteLine(astroSum);

    }
}