Lemma length_sublist1 {A: UU} (l1: list A) (l2: list A) : length l1 ≤ length (l1 ++ l2). Proof. rewrite length_concatenate. apply natlehnplusnm. Defined.
Require Import UniMath.Foundations.NaturalNumbers. Require Import UniMath.Combinatorics.Vectors.