proposition: Lemma odd_permV s : odd_perm s^-1 = odd_perm s.
proof: Proof. by rewrite -{2}(mulgK s s) !odd_permM -addbA addKb. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)