proposition: Lemma lift_subproof n h (i : 'I_n.-1) : bump h i < n.
proof: Proof. by case: n i => [[]|n] //= i; rewrite -addnS (leq_add (leq_b1 _)). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(path div)