using System;
using System.Linq;

class Program
{
    public void Solve()
    {
        string N = Console.ReadLine();
        if (0 <= N.Substring(1).Where(x => x != '3').Count())
        { Console.WriteLine(-1); }
        else
        { Console.WriteLine(N.Substring(1).Length); }
    }

    static void Main()
    {
        var solver = new Program();
        solver.Solve();
    }
}