using System;
using System.IO;
using System.Net;

namespace ConsoleApplication87
{
    class Program
    {
        static void Main(string[] args)
        {
            var wc = new WebClient();

            Directory.CreateDirectory("raw");
            Directory.CreateDirectory("dec");

            int pageCount = 1150;

            for (int i = 1; i <= pageCount; i++)
            {
                var fname = "page" + i.ToString("0000") + "_l.jpg";
                wc.DownloadFile(
                    "http://nblib.library.kz/elib/Sait" +
                    "/%D0%A0%D0%B5%D0%B4%D0%BA%D0%B8%D0%B5%20%D0%BA%D0%BD%D0%B8%D0%B3%D0%B8" +
                    "/01-10-2014/%D0%A2%D0%BE%D0%BC%206/1/assets/flash/pages/" + fname, "raw\\" + fname);
                Console.Write(".");
            }

            for (int i = 1; i <= pageCount; i++)
            {
                var fname = "page" + i.ToString("0000") + "_l.jpg";

                byte[] v = File.ReadAllBytes("raw\\" + fname);

                v[15] = (byte)(v[15] ^ 194);
                for (int j = 0; ; j++)
                {
                    int addr = j * 4 + 18;
                    if (addr >= v.Length)
                        break;
                    v[addr] = (byte)(v[addr] ^ (195 + j));
                }

                File.WriteAllBytes("dec\\" + fname, v);
            }
        }
    }
}