\documentclass[11pt]{article}
\usepackage[latin1]{inputenc}
\usepackage{t1enc}
\usepackage{a4}
\parindent0cm
\parskip1.5ex plus0.5ex minus0.5ex
\newtheorem{example}{Example}
\def\R{I\!\!R}
\def\vec{\mbox{vec}}
\def\eps{\varepsilon}

\begin{document}
\input{doctex0}
\setcounter{page}{1}
\input{doctex1}
\input{doctex2}
\input{doctex3}

\end{document}
