\documentclass{cis320}
\HWauthor{Student A}{studA@seas.upenn.edu}
\HWauthor{Student B}{studB@seas.upenn.edu}
\HWno{1}
\HWcourse{CIS 320}
%\HWextension
\begin{document}
\maketitle
\HWproblem
This is the solution to the first problem.
\HWproblem
\HWsubproblem
This is the solution to the second problem, first part.
\HWsubproblem
This is the solution to the second problem, second part.
\HWsubproblem
This is the solution to the second problem, third part.
\HWproblem
This is the solution to the the third problem.
\HWproblem
This is the solution to the the fourth problem.
\HWproblem
This is the solution to the the fifth problem.
\end{document}