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', '6291', '3939', '9569', 'u', '1635', '3359', '8335', 'n', '2799', '7359', 'k', 'm', '2817']

Answer: k, m, n, u, w


Question: ['l', '6313', '3199', 'w', '249', '8747', '7391', '3871', '173', 'x', 'o', '8647', '4413', '3645', '6123', '701', 'q', '2147', '4289', '7333', '533']

Answer: l, o, q, w, x


Question: ['e', '567', '7707', '2467', '7873', 'n', 'o', '3121', '1193', 'u', 'b', 'p', 't', 'r', '3493', 'a', '4389', 'v', '3645', 's', '8805', '4101', 'c', 'c', '1803', 'd', '4895', 'g', 'p', '173', '905']

Answer:
a, b, c, d, e, g, n, o, p, r, s, t, u, v