proposition: Lemma drop_append {A n} {ls ls' : list A} : drop n (ls ++ ls') = drop n ls ++ drop (n - List.length ls) ls'.
proof: Proof. revert n ls'; 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