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

namespace _01.Numbers1ToN
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());

            var result = 0;

            while (n > 0)
            {
                var lastNumber = n % 10;
                result += lastNumber;
                n /= 10;
            }

            Console.WriteLine(result);
        }
    }
}