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.

Ex Input:
['1429', '7273']

Ex Output:
-1


Ex Input:
['8489', 'h']

Ex Output:
h


Ex Input:
['m', 'o', 'b', '9867']

Ex Output:

b, m, o