\begin{tabbing}
(\=(((((((((D 1) \+
\\[0ex]CollapseTHEN (D 2))$\cdot$) 
\\[0ex]CollapseTHEN (AbReduce 4))$\cdot$) 
\\[0ex]CollapseTHEN (
\-\\[0ex]A\=bReduce 5))$\cdot$) \+
\\[0ex]CollapseTHEN (Try ((D 6) 
\\[0ex]CollapseTHEN (Eq))$\cdot$))$\cdot$) 
\\[0ex]CollapseTHEN (
\-\\[0ex](Auto\_aux (first\_nat 1:n) ((first\_nat 1:n),(first\_nat 3:n)) (first\_tok :t) inil\_term)))$\cdot$
\end{tabbing}