How to get to use {align} with an unusual document class?

Question

So I'm required to use a particular documentclass, "llncs", which for some reason is preventing me from using {align}. Is there an alternative that I can use?

The beginning of my tex file

\documentclass{llncs}

My tex part with errors is

\begin{align*}
\forall q \in S \begin{cases}
PRUNE(I_{p_j}) \iff d(p_j,q) - r \ge d_{m_j}\\
PRUNE(O_{p_j}) \iff d(p_j,q) + r < d_{m_j}
\end{cases}
\end{align*}

Answer 1

I'm not familiar with the llncs document class, and it doesn't seem to be included in the TeXLive distribution. That said, if you can't load the amsmath package via a \usepackage statement after the \documentclass directive, the following might do the job for you:

\RequirePackage{amsmath}
\documentclass{llncs}
% rest of document