proposition: Lemma canword1 : canword (1 : 'S_n.+1) = [::].
proof: Proof. Proof using. have:= canword_reduced 1. by rewrite unfold_in canwordP length1 eq_sym => /nilP. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(fingroup perm morphism presentation) mathcomp(ssralg poly ssrint) permcomp tools permuted combclass congr