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:
['1449', 'a', '6261', '303', '4651', 'n', 'u', '1595']
answer:
a, n, u


question:
['4641', '2881', 'c', '4827']
answer:
c


question:
['2369', 'c', '9391', 'p', '4437', 'k', '2329']
answer:

c, k, p