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:
['r', '9489', 'e', 'n', '6323', 'd', '3163', '265', '8587', '7891']
answer:
d, e, n, r


question:
['7591', '1403']
answer:
-1


question:
['6515', 'n', 'k', 'l', '6295', '8519', '4879', '4273', 'i', '8735', '1817', 'u', '4271', 's', 'n', 'q', '2729', 'a', '9413', '2027']
answer:

a, i, k, l, n, q, s, u


