using System;
using System.Linq;
using System.Collections.Generic;
using System.Text;
using static System.Console;
using static System.Math;

class Program
{
    static void Main(string[] args)
    {
        string s = ReadLine();
        int sum = 0;
        for (int i = 0; i < s.Length; i++)
        {
            sum += s[i] - '0';
        }
        WriteLine(sum);
    }
}