\begin{tabbing}
((\% Generalize \% 
\\[0ex]A\=ssert $\forall$$j$,$s$:$\mathbb{N}$. ($s$ $<$ $j$) $\Rightarrow$ $P$($s$)) \+
\\[0ex]C\=ollapseTHEN (IfLabL \+
\\[0ex]
\\[0ex][`assertion`,Id 
\\[0ex];`main`,((InstHyp [$i$ + 1;$i$] ({-}1)) 
\-\\[0ex]CollapseTHEN (
\-\\[0ex](Auto\_aux (first\_nat 1:n) ((first\_nat 2:n),(first\_nat 3:n)) (first\_tok :t) inil\_term)))$\cdot$]
\\[0ex]))$\cdot$
\end{tabbing}