proposition: Lemma drop_all {A n} {ls : list A} (H : List.length ls <= n) : drop n ls = nil.
proof: Proof. revert n H; induction ls; drop_take_t. 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