%% 
%%  Example 01-02-5 
%%  Copyright (C) 2017 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{110.31393pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{xcolor}
%StopShownPreambleCommands
\begin{document}
\colorbox{yellow}{$f(x)=\prod_{i=1}^{n}
                   \left(i-\frac{1}{2i}\right)$}
\end{document}
