using System;
using System.Text.RegularExpressions;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            string n = Console.ReadLine();
            Match m = Regex.Match(n, "^13+$");
            if (m.Success)
            {
                Console.WriteLine(m.Length-1);
            }
            else
            {
                Console.WriteLine(-1);
            }

        }
    }
}