\begin{tabbing}
(\=(Assert (($a$+$n$) {-} $n$) = (($b$+$n$) {-} $n$)) \+
\\[0ex]CollapseTHENM ((Auto\_aux (first\_nat 1:n
\-\\[0ex]) ((first\_nat 2:n),(first\_nat 3:n)) (first\_tok :t) inil\_term)))$\cdot$
\end{tabbing}