proposition: Lemma Npow2_ge_one: forall sz : nat, 1 <= Npow2 sz.
proof: Proof. intros. apply N.lt_succ_r. rewrite <- N.add_1_l. apply N.lt_sub_lt_add_l. apply Npow2_gt_zero. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat List Bedrock.Word Coq.ZArith.ZArith Coq.micromega.Psatz NArith NArithRing