proposition: Lemma drop_dropS {A} y (ls : list A) : drop 1 (drop y ls) = drop (S y) ls.
proof: Proof. rewrite drop_drop. rewrite Nat.add_1_r. reflexivity. Qed.
imports: Fiat.Common.Coq__8_4__8_5__Compat Coq.ZArith.ZArith Coq.Lists.List Coq.Lists.SetoidList Coq.Bool.Bool Fiat.Common Fiat.Common.List.Operations Fiat.Common.Equality Fiat.Common.List.FlattenList Fiat.Common.LogicFacts