using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace template
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = Console.ReadLine();
            int ret = 0;
            for (int i = 0; i < s.Length; i++) ret += int.Parse(s[i].ToString());
            Console.WriteLine(ret);
        }
    }
}