proposition: Lemma leq_div2r d m n : m <= n -> m %/ d <= n %/ d.
proof: Proof. have [-> //| d_gt0 le_mn] := posnP d. by rewrite leq_divRL // (leq_trans _ le_mn) -?leq_divRL. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq)