proposition: Lemma addmK m : cancel (+%MM^~ m) (-%MM^~ m).
proof: Proof. by move=> m' /=; apply/mnmP=> i; rewrite !mnmE addnK. 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