documentclass[a4paper,11pt]{book}
 usepackage[italian]{babel}
 usepackage[latin1]{inputenc}
 usepackage[T1]{fontenc}
 usepackage{amssymb,amsmath}
 usepackage{amsthm}
 usepackage{graphicx}
 theoremstyle{plain}
 newtheorem{thm}{Teorema}[section]

 usepackage{blindtext}%
 usepackage{etoolbox}%


setcounter{tocdepth}{3}
setcounter{secnumdepth}{3}

pagestyle{myheadings}

begin{document}
tableofcontents


chapter{First Chapter}
 section{First section of the first chapter }

 end{document}