\begin{tabbing}
(\=(((((Unfold `decidable` 0) \+
\\[0ex]CollapseTHEN (DNth 2 0))$\cdot$) 
\\[0ex]CollapseTHENM (D 0))$\cdot$) 
\\[0ex]
\\[0ex]CollapseTHEN ((Auto\_aux (first\_nat 1:n) ((first\_nat 1:n),(first\_nat 3:n)) (first\_tok :t
\-\\[0ex]) inil\_term)))$\cdot$
\end{tabbing}