proposition: Lemma inject1_proof n (i : 'I_n.+1) : (n - i + i = n)%N.
proof: Proof. by rewrite subnK // -ltnS. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(order fingroup perm ssralg zmodp poly ssrint) mathcomp(matrix vector) mathcomp(bigenough) ssrcomplements freeg