namespace Patch
{
    class Program
    {
        static void Main(string[] args)
        {
            string sSource = "XPEH";
            string sDest = "HEPX";

            foreach (string FileName in args)
            {
                FileStream fsSource = new FileStream(FileName, FileMode.Open, FileAccess.ReadWrite);

                int iByte;

                do
                {
                    iByte = fsSource.ReadByte();

                    if (iByte > -1)
                    {
                        if (iByte == sSource[0])
                        {
                            bool bIsEqual = false;

                            long lOffset = fsSource.Position;

                            foreach (char cByte in sSource)
                            {                               
                                if (iByte > -1)
                                {
                                    bIsEqual = (iByte == (int)cByte);
                                    if (!bIsEqual)
                                    {
                                        break;
                                    }
                                }

                                iByte = fsSource.ReadByte();
                            }

                            if (!bIsEqual)
                            {
                                fsSource.Seek(lOffset, SeekOrigin.Begin);
                            }
                            else
                            {
                                fsSource.Seek(lOffset - 1, SeekOrigin.Begin);

                                foreach (char cByte in sDest)
                                {
                                    fsSource.WriteByte((byte)cByte);
                                }

                            }
                        }
                    }

                } while (iByte > -1);

                fsSource.Close();
            }
        }
    }
}