class Program
{
    static void Main(string[] args)
    {
        string line = System.Console.ReadLine().Trim();

        int count = 0;

        for(int i=0;i<line.Length;i++)
        {
            int  result = 0;

            if(int.TryParse(line[i].ToString(), out result))
            {
                count += result;
            }

        }
        System.Console.WriteLine(count);
    }
}