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:
['2521', '8027', 'm', '193', '615', 'l', '1947', '5949', '6307', 'r', '1015', '743', 'v', '6949', 'b', 'g', '8841', 'c', 'b', '2879']

Ex Output:
b, c, g, l, m, r, v


Ex Input:
['s', 'u']

Ex Output:
s, u


Ex Input:
['f', '6551', '4443', 'r', '2679', '5927', 'z', '219', 'b', 'q', '7403', 'i', 'v']

Ex Output:

b, f, i, q, r, v, z