proposition: Lemma length_maxpermMr s : length (s * maxperm) = 'C(n, 2) - length s.
proof: Proof. rewrite /length invset_maxpermMr cardsD card_Delta. by have /setIidPr -> := invset_Delta s. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr