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:
['8489', 'h']
answer:
h


question:
['y', 'b', 'r', 'f', '3745', 'n', '2921', '8133', 'r']
answer:
b, f, n, r, y


question:
['w', '1999', '5689', 'q', '6639', '4177', 'c', 's', 'i', 'q', 's', 'r', 'o', 'v', 'j', '9571', 'r', '3169', 'b', '2719', 'i']
answer:

b, c, i, j, o, q, r, s, v, w


