%%Do not change font size
\documentclass[12pt]{article}
\usepackage{amsthm,amssymb,fullpage}

%Macros
\newtheorem{lemma}{Lemma}
\newtheorem{theorem}[lemma]{Theorem}
\newtheorem{informaltheorem}[lemma]{Informal Theorem}
\newtheorem{informallemma}[lemma]{Informal Lemma}
\newtheorem{corollary}[lemma]{Corollary}
\newtheorem{definition}[lemma]{Definition}
\newtheorem{proposition}[lemma]{Proposition}
\newtheorem{question}{Question}
\newtheorem{remark}[lemma]{Remark}
\newtheorem{claim}{Claim}
\newtheorem{fact}{Fact}
\newtheorem{challenge}{Challenge}
\newtheorem{observation}{Observation}
\newtheorem{openproblem}{Open Problem}
\newtheorem{openquestion}{Open question}

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\newcommand{\eeq}{\end{equation}}
\newcommand{\beas}{\begin{eqnarray*}}
\newcommand{\eeas}{\end{eqnarray*}}

\newcommand{\poly}{\mathrm{poly}}
\newcommand{\eps}{\epsilon}
\newcommand{\e}{\epsilon}
\newcommand{\polylog}{\mathrm{polylog}}
\newcommand{\rob}[1]{\left( #1 \right)} %Round Brackets
\newcommand{\sqb}[1]{\left[ #1 \right]} %square Brackets
\newcommand{\cub}[1]{\left\{ #1 \right\} } %curly brackets
\newcommand{\rb}[1]{\left( #1 \right)} %Round
\newcommand{\abs}[1]{\left| #1 \right|} %| |
\newcommand{\zo}{\{0, 1\}}
\newcommand{\zonzo}{\zo^n \to \zo}
\newcommand{\zokzo}{\zo^k \to \zo}
\newcommand{\zot}{\{0,1,2\}}

\newcommand{\en}[1]{\marginpar{\textbf{#1}}}
\newcommand{\efn}[1]{\footnote{\textbf{#1}}}

%End macros

\begin{document}

\begin{center}
\begin{tabular}{|c|}
\hline
CSG399: Gems of Theoretical Computer Science. \hspace{3cm} Lecture 1. Jan.~9, 2009.\\
Instructor: Emanuele Viola \hfill Scribe: Your name\\
\\
{\bfseries \large Preliminaries}\\ \hline
\end{tabular}
\end{center}

\section{Write here}

Write here. Example: For every $x \in \zo^n$, we have:
$$E_e [X] \leq \Pr_{y} \left[ \frac1y = 3\right],$$
and so on.

\begin{lemma}[Insight]
There is $x \leq a$ such that: bla.
\end{lemma}
\begin{proof}
Bla bla.
\end{proof}

\end{document}