proposition: Lemma leq12 a b c : a <= b <= c -> a <= b.
proof: Proof. by case/andP. Qed.
imports: Coq(ssreflect ssrbool ssrfun Eqdep) mathcomp(ssrnat seq eqtype choice fintype) pcm(options axioms) Coq(Classes.Morphisms Program.Basics Program.Tactics) Coq(Relations)