using System;

​

public class Program

{

    public static void Main()

    {

        var n = int.Parse(Console.ReadLine());

        var sum =0;

        while(true)

        {

            var digit = n % 10;

            sum +=digit;

            n/=10;

            if(n == 0)

            {

                break;

            }           

        }       

        Console.WriteLine(""+sum);

    }

}