proposition: Lemma zle_pr2 x y: inc x BZp -> inc y BZms -> y <z x.
proof: Proof. move => pa pb; move:(BZp_sg pa) (BZms_sg pb) => pc pd. move:(BZp_sBZ pa) (BZms_sBZ pb) => pa' pb'. split; first by split => //; constructor 2. move /(congr1 Q); rewrite pc pd; fprops. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)