using System;
using System.IO;
using System.Linq;

namespace ConsoleApp4
{
    class Program
    {
        static void Main()
        {
            var C =  Console.ReadLine();
            if (C.Contains("0"))
            {
                var _contains10 = C.Length;
                var _notContains10 = C.Split("0").Length - 1;
                var ans = _contains10 - _notContains10 - 1;
                Console.WriteLine(ans);
            }
            else
            {
                Console.WriteLine(C.Length - 1);
            }

        }
    }
}