\newcommand{\defineUnit}[2]{\setbeamertemplate{slide #1}{{#2}}}
\newcommand{\showUnit}[1]{\usebeamertemplate{slide #1}}

\defineUnit{titel}{%
\begin{frame}
    \titlepage
\end{frame}
}

\input{intro.tex}
\input{basics.tex}
\input{logic.tex}
\input{growth.tex}
\input{combinatorics.tex}
\input{graphs.tex}
\input{algebra.tex}