destruct i. eexists; reflexivity.
destruct i. eexists; reflexivity.
destruct i. eexists; reflexivity.
destruct i. eexists; reflexivity. omega. Qed.

Lemma SixteenWR_int s i: (0<=i<16)%nat -> exists ii, nth i (SixteenWordRep s) Vundef = Vint ii.
intros. destruct s as [[[? ?] ?] ?]. simpl.