\documentclass{amsart}
%\documentclass{article}
  
  \usepackage[all]{xy}
  
  % \usepackage{amsmath,amssymb,enumerate}
  \usepackage{epsf,epsfig,amsfonts,graphicx,color}
  
  \usepackage{url}
   
 \def\R{\mathbb R}
\def\bP{\mathbb P}
\def\C{\mathbb C}
 \def \E {\mathbb E}
 \def \V {\mathbb V}
  \def \W {\mathbb W}
 \def \S {\mathbb S}
  \def \I {\mathbb I}
 \def \Z {\mathbb Z}
\def\N {\mathbb N}
\def\T {\mathbb T}
  
 \def\on{orthonormal }
\def \nbhd {neighborhood }
\def \nbhds {neighborhoods }
\def\Ri{Riemannian }
\def\Ri{ subRiemannian }

\newtheorem{theorem}{Theorem}[section]
\newtheorem{proposition}{Proposition}[section]
\newtheorem{corollary}{Corollary}[section]
\newtheorem{lemma}{Lemma}[section]
\newtheorem{definition}{Definition}[section]
\newtheorem{remark}{Remark}[section]
\newtheorem{example}{Example}[section]
\newtheorem{conj}{Conjecture}

\newtheorem{exer}{Exercise}[section]

\newcommand{\dd}[2] { {{\partial #1}   \over {\partial #2}} }

\usepackage{amsmath,amssymb}
\usepackage{graphicx}

\begin{document}

\title{HW 2.}
 
 HELLO 


\date{today}

\end{document}