(* Conversion from list to kn *)
Fixpoint kn2l (n : nat) : kn n -> list K :=
match n return (kn n -> list K) with
| 0 => fun x => nil
| S n1 => fun v => let (a, v1) := v in a :: kn2l n1 v1
end.

Lemma kn2ll2knE n x : l2kn n (kn2l n x) = x.