proposition: Lemma odd_permJ s1 s2 : odd_perm (s1 ^ s2) = odd_perm s1.
proof: Proof. by rewrite !odd_permM odd_permV addbC addbK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)