proposition: Lemma block_mxKdr : drsubmx A = Adr.
proof: Proof. by rewrite /drsubmx col_mxKd row_mxKr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg countalg finalg zmodp)