proposition: Lemma nxP n : nxown_spec n (nxown n).
proof: Proof. by case: n=>[|n]; [apply: nxZ | apply: (@nxS _ n)]. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq) pcm(options prelude pred) pcm(pcm morphism natmap)