\documentclass[proceedings]{dmtcs}

\author{First Author\addressmark{1}\thanks{I am not supported.}{\ }
  \and Second One\addressmark{2}\thanks{But he is!}{\ }
  \and Someone Else\addressmark{2}}
\title[Formatting a submission for DMTCS]{How to format a submission}
\address{\addressmark{1}INRIA \& LORIA, campus scientifique, BP 239,
  F-54506 Vand{\oe}uvre l\`es Nancy, France\\
\addressmark{2}Alma Mater, campus universalis, terra incognita}
\keywords{some well classifying words}

\begin{document}
\maketitle
\begin{abstract}
  This abstract should be some brief description of your work and how
  it advances our science.
  {\small please also repeat in the submission form}
\end{abstract}
\begin{proof}
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
\end{proof}

This is intermediate text.

\begin{proof}[of the Main Theorem]
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
    Some text that explains why this is so and not otherwise.
\end{proof}
\end{document}
