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:
['9947', '3353', '8643', '4621', '4857', 'y', '7075', 'c', '8911']

Ex Output:
c, y


Ex Input:
['h', 'g', '4563', 'v', 'm', '107']

Ex Output:
g, h, m, v


Ex Input:
['6299', 'k', '6961', 'a']

Ex Output:

a, k