[Tex/LaTex] Missing begin document in latex file with multiple chapters


Interesting point is that until yesterday I ran this code easily without getting any error but suddenly it keep sending the error of missing begin document. I see some similar question and it was suggested to copy the file as some special format and I don't know how to do that. My file has multiple chapters and I type other part of my works in 5 other latex file.
Would you please help me with that?
Here is my code:

% all required packages


           \markboth{#1}{\thechapter\ #1}}
            \markright{\thesection\ #1}}

    \chapter{Preliminaries and Notions}
    \chapter{Backbone Colouring}
    \chapter{Algorithm for Finding Backbone}

\addcontentsline{toc}{chapter}{Table of Figures}

and here is the error that I got, I copy and paste the part of it:

   ! LaTeX Error: Missing \begin{document}.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
l.1 +
% Copyright (c) 2012
You're in trouble here. Try typing <return> to proceed.
If that doesn't work, type X <return> to quit.
Missing character: There is no + in font nullfont!
Overfull \hbox (20.0pt too wide) in paragraph at lines 1--5
("C:\Program Files (x86)\MiKTeX 2.9\tex\latex\base\report.cls"
Document Class: report 2007/10/19 v1.4h Standard LaTeX document class
("C:\Program Files (x86)\MiKTeX 2.9\tex\latex\base\size12.clo"
File: size12.clo 2007/10/19 v1.4h Standard LaTeX file (size option)

Best Answer

You have a + on line one of your file which is not in a comment so TeX tries to typeset it before the \documentclass (and before \begin{document}). Hence the error message.