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: ['3947', '4809', 'b', 'a', '4769', '4179', '535', '5965', 'f', 'j', '2265', 'w', '3103', 'u']

Answer: a, b, f, j, u, w


Question: ['6955', '721', '2763', '8121', '9109', '6341', 'p', 't', 'x', '6963', '1137', 'z', 'u', '1949', '7029', 't', '9539', 'a', 'u', '1873']

Answer: a, p, t, u, x, z


Question: ['s', '2449', '3289', 'r', 'r', 'k', 'q', '2203', 'x', 'q', 'f', '8747', 'a', 'k', 'a', 'b', '3297', '1729', '5717', '1035', '8491', 'm', 'v', '4843', '8377', '4089', 'h', '3407', 'r']

Answer:
a, b, f, h, k, m, q, r, s, v, x