using System;

namespace yukicoder
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var n = Console.ReadLine();
            var result = 0;

            foreach (var item in n)
            {
                var a = 0;
                result += int.TryParse(item+"", out a) ? a : 0;
            }

            Console.WriteLine(result);
        }
    }
}