proposition: Lemma allpairs_bseqP f s (s' : m.-bseq U) : @size rT (allpairs f s s') <= n * m.
proof: Proof. by rewrite size_allpairs; apply/leq_mul/size_bseq/size_bseq. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype path)