\begin{tabbing}
(\=(((((InstHyp [$a$;$b$] 6) \+
\\[0ex]CollapseTHENM (Unfold `strict\_part` 0))$\cdot$) 
\\[0ex]CollapseTHENM (
\-\\[0ex]P\=roveProp))$\cdot$) \+
\\[0ex]CollapseTHEN ((Auto\_aux (first\_nat 1:n) ((first\_nat 1:n),(first\_nat 4:n
\-\\[0ex])) (first\_tok :t) inil\_term)))$\cdot$
\end{tabbing}