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: ['7591', '7521', 'm', '1429', 'x']

Answer: m, x


Question: ['7799', '8163', '3389', 'x', 'k', 'm', '6085', 'f', '1131']

Answer: f, k, m, x


Question: ['c', '3411', '4011', '6811', 'c', 'a', '7693', '9521', 'b', '5505', 'v', 'b', 'g', 'q', 'm', 'w', '2221', '2281', '385', 'h', 'm', '8415']

Answer:
a, b, c, g, h, m, q, v, w