using System;

public class Program

{

    public static int DigitSum( int n )

    {

        int x, y, z;

        x = n % 10;

        y = (n/10)%10;

        z = n/100;

        return (x + y + z); 

    }

    public static void Main()

    {

    int x;

    x = int.Parse(Console.ReadLine());  

    Console.WriteLine(DigitSum (x));

    }

}