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.

Q: ['6769', '1057', '1021', 'n', '8231', '9173', '8123', 'a', '6053', 'q', 'y', '883', 'r', '1215', 'x', 'o', '9531']

A: a, n, o, q, r, x, y
****
Q: ['p', '2923', 'e', 'k', '5433', '605', '5079', 'k', 'p', 'x', '4845', '4099', '6795']

A: e, k, p, x
****
Q: ['b', '2567', '1571', 'h']

A:
b, h
****