proposition: Lemma head_sternD u v n: head 0 (sternD u v n) = u.
proof: Proof. by elim:n => // n {2} <- /=; case:(sternD u v n) => // [] c []. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq choice fintype order bigop ssralg) mathcomp(div ssrnum ssrint rat prime path binomial) mathcomp(tuple finset) gaia(fibm)