\begin{tabbing}
(\=(((((((HypSubst ({-}1) 0) \+
\\[0ex]CollapseTHENM (RWO "length\_append" 0))$\cdot$) 
\\[0ex]CollapseTHENA (
\-\\[0ex](Auto\_aux (first\_nat 1:n) ((first\_nat 1:n),(first\_nat 3:n)) (first\_tok SupInf:t
\\[0ex])\= inil\_term)))$\cdot$) \+
\\[0ex]CollapseTHEN (InstConcl [$\parallel$$L$$\parallel$]))$\cdot$) 
\\[0ex]CollapseTHEN (
\-\\[0ex](Auto\_aux (first\_nat 1:n) ((first\_nat 2:n),(first\_nat 3:n)) (first\_tok SupInf:t
\\[0ex]) inil\_term)))$\cdot$
\end{tabbing}