Lemma loop1_aux_lemma1: forall i b, (0 <= i < Zlength b) -> Zlength b <= 16 -> upd_Znth i (map Vint (sublist 0 i b) ++ list_repeat (Z.to_nat (16 - i)) Vundef) (Vint (Znth i b)) = map Vint (sublist 0 (i+1) b) ++ list_repeat (Z.to_nat (16 - (i+1))) Vundef.