In this task, you are given an input list A comprising of numbers and alphabets. You need to extract and sort the unique alphabets in the list. The alphabets in the input list will only be in lowercase. Return -1 if there is no alphabet in the input list.
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Question: ['6709', 't', 'n', 'k', '991', 'a', '8899', '3563', '527', 'm', '4599', '6679', 'm', 'x', 'f', 'o', '3275', 'x', '677', 'b', '3329', '3593', '5183', '5753', 'u', '6045', '2607', 'y', '9873']

Answer: a, b, f, k, m, n, o, t, u, x, y


Question: ['s', '2507', '3091', 'g', '7643', '2573', 'w', 'r', '1977', 'q', 'c', 'j', '1335', '9671', '7317', '567', '2041', '5777', 'w', 'm']

Answer: c, g, j, m, q, r, s, w


Question: ['a', 'v', '9109', 'm', 'a', '3777', '8035', 'm', 's', '3525', '5721', 'a', 'j', '2769', 'd', '8549', '5743', 'c', '517', '4281', 'n', '4585', '4125', '9805', '8357', 'x']

Answer:
a, c, d, j, m, n, s, v, x