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: ['6249', '1235']

Answer: -1


Question: ['5957', 'd', 'i', 'b', 'e', '5565', 'c', 'i', '2919']

Answer: b, c, d, e, i


Question: ['r', '7205', 'b', '5587', 'x', '6647', '9287']

Answer:
b, r, x