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: ['2521', '8027', 'm', '193', '615', 'l', '1947', '5949', '6307', 'r', '1015', '743', 'v', '6949', 'b', 'g', '8841', 'c', 'b', '2879']

Answer: b, c, g, l, m, r, v


Question: ['331', '125', 'u', 'a', 's', '6995', 'i', '3613', '9727', '7087', 'l', 'b', '8291', '813', 'i', '1169', '2159', 'd', '1451', 'q']

Answer: a, b, d, i, l, q, s, u


Question: ['b', 'g', 'v', '7171', 'q', 'h', 'z', 'e', 'a', '2905', '4139', 'd', 'p', 'l']

Answer:
a, b, d, e, g, h, l, p, q, v, z