fact: Fixpoint Ack (m n : nat) : nat := match m with | O => n.+1 | p.+1 => let fix Ackm (n : nat) := match n with | O => Ack p 1 | S q => Ack p (Ackm q) end in Ackm n end.
imports: Coq(Lia) Coq(Program.Wf Arith) hydras(ssrnat_extracts)