How to make an \input file build on its own?

Question

I am working on an article in LaTeX that I am splitting into multiple files with \input commands. Each section is in one such file of its own. Is there a way to make these files build on their own while still being able to build the main document that \inputs them?

Something like this:

\if<this is top level>
  \documentclass{article}
  \begin{document}
\fi
Section text goes here
\if<this is top level>
\end{document}
\fi