instruction:
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.
question:
['a', 'a', 'b']
answer:
a, b


question:
['5075', '9169', '4659', '7605']
answer:
-1


question:
['5529', 'd', '5685', '7277', 'e', '2739', 'v', 'n', 'n', '7609', 'c', 'a', '699', 'n', '2883', 'b', 'a', '5607', '301', 's', 'n', '7435', 'g', 'x', '5955', '9237', '8733', '9675', 'b', '7741', '7853', '7995', '8427', '7799', 'v', '7847', 'y', '955', 'o', 'v', '4355', 'y', 'y', 'r']
answer:

a, b, c, d, e, g, n, o, r, s, v, x, y