<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">\documentclass{ppex}
\nonstopmode
\usepackage {xy}
\pagestyle{empty}
\setlength\textwidth{183.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage {xy}
\[\begin{xy} 0;&lt;5mm,0mm&gt;:
 0*{DL} ,(2,0)*{DR} ,&lt;0cm,1cm&gt;*{UL} ,(2,2)*{UR}
 ,0+(4,0)="NO"*{\mathtt{DL}}
 ,"NO"+(2,2)="SUR"*{\mathtt{UR}}
 ,"SUR"-&lt;1cm,0cm&gt;*{\mathtt{UL}}
 ,"SUR"-(0,2)*{\mathtt{DR}}
\end{xy}\]
\end{document}
</pre></body></html>