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.

Q: ['4749', '4607', '625', '6907', 't', 'b', '8479', '6505', 'r']

A: b, r, t
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Q: ['n', '7489', 'n', 'n', '9787', '7829', 'n', '3481', 'v', 'l', '8927', 'c', 'm', 'd']

A: c, d, l, m, n, v
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Q: ['1137', '1919', '7825', '7035', '8609', '6385', 's']

A:
s
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