Given the task definition and input, reply with output. In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Five vowels are commonly cited including a,e,i,o, and what final letter?, Context: In Eastern Catalan (except Majorcan), unstressed vowels reduce to three: /a e ɛ/ > [ə]; /o ɔ u/ > [u]; /i/ remains distinct. There are a few instances of unreduced [e], [o] in some words. Alguerese has lowered [ə] to [a].
u