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', 'n', '729', '2491', 'n', 'x', '915', '1869', 'z', '8491', '9947', '561', '829', 'n', 't', 'i']

Answer: i, n, t, w, x, z


Question: ['6209', 'x', 'j', 'w', '7965', '4905', '6297', '4291', '7183', 'a', 'l', '5267', 'r', '5935', 'a', '7865', 'h', 'p', '6117', 'a', 'y', 'y', 't', 'v', '7271', 'e', 'e', 'z', 'i', 'l', '4731', '2059', 'm', '5703', 'k', 'f', '8125', 'e', '7569', 'r', '2287', '593']

Answer: a, e, f, h, i, j, k, l, m, p, r, t, v, w, x, y, z


Question: ['o', 'c', '6469', 'x', '8815', '4441', '6193', 'u', 'm', 'a', '9879', 'p', '8335', 'c', 'z']

Answer:
a, c, m, o, p, u, x, z