%% 
%%  Example 06-05-1 
%%  Copyright (C) 2016 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{158.31393pt}
\setlength\parindent{0pt}
\usepackage[T1]{fontenc}
%StartShownPreambleCommands
\newcommand*\threesim{%
  \mathrel{\vcenter{\offinterlineskip
  \hbox{$\sim$}\vskip-.35ex%
  \hbox{$\sim$}\vskip-.35ex\hbox{$\sim$}}}}
%StopShownPreambleCommands
\begin{document}
$\threesim ABC$
\end{document}
