using System;

public class Hello
{
    static void Main()
    {
        var s = Console.ReadLine().Trim();
        Console.WriteLine(getAns(s));
    }
    static long getAns(string s)
    {
        if (s == "1") return -1;
        var sL = s.Length;
        if (s[0] != '1') return -1;
        if (s.Replace("3", "") != "1") return -1;
        return sL - 1;
    }
}