namespace _01._Crooked_Digits
{
    using System;
    using System.Numerics;
    class Program
    {
        static void Main(string[] args)
        {
            string number = Console.ReadLine();
            string numberWithoutDot = number.Replace(".", string.Empty);
            Decimal newNumber = Decimal.Parse(numberWithoutDot);
            newNumber = Math.Abs(newNumber);
            string finalNumberAsString = newNumber.ToString();

            int currentNum = 0;
            int sum = 0;

            for (int i = 0; i < finalNumberAsString.Length; i++)
            {
                currentNum = finalNumberAsString[i] - 48;
                sum += currentNum;
            }

            if (sum > 9)
            {
                string finalNumber = sum.ToString();
                int finalNum = 0;
                int finalSum = 0;

                for (int i = 0; i < finalNumber.Length; i++)
                {
                    finalNum = finalNumber[i] - 48;
                    finalSum += finalNum;
                }
                Console.WriteLine(finalSum);
            }
            else
            {
                Console.WriteLine(sum);
            }
        }
    }
}