\documentclass[letterpaper]{article}
\newcommand{\half}{\frac{1}{2}}

\usepackage[latin1]{inputenc}
\usepackage{calc}
\usepackage{setspace}
\usepackage{graphicx}
\usepackage{multicol}
\usepackage[normalem]{ulem}
\usepackage{amsmath}
%% Please set your language here
\usepackage[english]{babel}
\usepackage{color}
\usepackage{mathrsfs}
\usepackage[pdftex,bookmarks=true,bookmarksnumbered=true]{hyperref}

\begin{document}
\tableofcontents
\section{section1}
\subsection{subsection 1.1}
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\section{section2}
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\subsection{subsection\&2.1}
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\end{document}
