proposition: Lemma size_psi a b c n d: (size [a, b, c] <= size (cons a b c n d))%N.
proof: Proof. by rewrite ltnS maxn0 !maxnA leq_maxl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(fintype bigop)