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: ['y', 'g', '107', '4899', '6357', '9777', 'k', '1865', '7029', 'q', 'x', '7051', 's', '6125', '4285', '2731', 'z', 'a', '737', '6137']

Answer: a, g, k, q, s, x, y, z


Question: ['s', 'w', 'c', '4137', 't', '2437', '349', 'h', '4539', 't', 'b', 'y', 'q', 't', '9087', 'c', '9489', '6285', '6247', '8353', 'n', 't', '8661', 'p', 'z', 'p', '773', 'w', 'q', '8081', 'r', 'u', 'z', 'k', 'a', 'b', '7513', '5549', '5325', '1101', 's', '6507', '3317']

Answer: a, b, c, h, k, n, p, q, r, s, t, u, w, y, z


Question: ['h', '3307', '9703', 'q', 'e', 'r', '3705', 'm', '4179', 'c', '9375', 's', '1515', '2137', '7853', '6441', '535', 't', 'u', 'e', 'a', 'l', 'u', '6017', '1479', '3495', 'w', 'u', '5451', 'u', 'x', '8085', 'a', '8685']

Answer:
a, c, e, h, l, m, q, r, s, t, u, w, x