The Latin alphabet of the time still lacked the letters ⟨j⟩ and ⟨w⟩, and there was no ⟨v⟩ as distinct from ⟨u⟩; moreover native Old English spellings did not use ⟨k⟩, ⟨q⟩ or ⟨z⟩. Along with k and z, what Latin letter was not used in Old English?