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: ['3147', '9807', '5313', '6311', '737', '1555', '5803', '3437', '5665', '3973', 'o', 'f', '7871', '1721', '7833', '2933', 'b', 'b', 'n', 'm', 'k']

Answer: b, f, k, m, n, o


Question: ['w', '8777', 'y', 'e', '8015', 't', 'w', '53', '9149', 'e', 'k', '1837', 'b', 's', '4007', '4905']

Answer: b, e, k, s, t, w, y


Question: ['v', '459', 'y', '4663', '2047', '9523', '2295', 'l', 'e', '4547', 'q', 'n', '3777', 'n', 'y', '3009', 'h', 'e', '7475', '4007', 'b', 'm']

Answer:
b, e, h, l, m, n, q, v, y