using System;
using System.Linq;

namespace lv1_804
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = Console.ReadLine();

            if (s.Length == 1)
            {
                Console.WriteLine(-1);
                return;
            }


            if (s[0] == '1')
            {
                if (s.Skip(1).All(x => x == '3'))
                    Console.WriteLine(s.Length - 1);
                else Console.WriteLine(-1);
            }        
            else Console.WriteLine(-1);
        }
    }
}