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: ['w', 'n', '729', '2491', 'n', 'x', '915', '1869', 'z', '8491', '9947', '561', '829', 'n', 't', 'i']

Answer: i, n, t, w, x, z


Question: ['w', 'o', 'l', '1857', 's', 'q', 'j', 'e', '5945', 'g', 'l', '9563', 'e', 'u', '7633', '7977', '4943', 'y', '5621', 'f', '1653', 'c', 'l', '2843', '2125', '7731', '5257', '5667', 'b', 'b', '5765', 'a', 't', '8163', '9785', '5385']

Answer: a, b, c, e, f, g, j, l, o, q, s, t, u, w, y


Question: ['5987', 'q', 'o', '4173', '7141', 'b', '4575', '7909', 'r', 'i', '4617', 'u', 'k', 'b', 'a', '4191', 'u', 'l', 'a', '2581', 'r', '3009', '7669', 'q', '2679', 'o', 'q', '5025', '9941', 'p', '2281', 'v', 'a', '3455', '7723', 'c', '3979']

Answer:
a, b, c, i, k, l, o, p, q, r, u, v