proposition: Lemma ctree_cons_proper h t1 t2 t3 : ctree_proper h t1 -> ctree_proper h t2 -> ctree_proper h t3 -> ctree_proper h.+1 (ctree_cons t1 t2 t3).
proof: Proof. by move=> t1ok t2ok t3ok; rewrite ctree_cons_spec; case: ifP. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq) fourcolor(color)