using System;
using System.Linq;

namespace Lecture4
{
    class Program
    {
        static void Main(string[] args)
        {
            string line = Console.ReadLine();
            int number = 0;
            for (int i = 0; i < line.Count(); i++)
            {
                number += int.Parse(line.Substring(i, 1));
            }

            Console.WriteLine(number);
        }
    }
}