using System;

public class Program

{

    public static void Main()

    {

        var fileName = "p-zkuPs1E9qU2IpK_iSfydTQ_583d1011-034b-4928-a875-5c70fdaba5a9.pdf";

        var fileId = fileName.Substring(fileName.Length - 40, 36);

        Console.WriteLine(fileId);

    }

}