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: ['w', 'n', '729', '2491', 'n', 'x', '915', '1869', 'z', '8491', '9947', '561', '829', 'n', 't', 'i']

A: i, n, t, w, x, z
****
Q: ['8879', 'x', '1383', '4925', '2867', 'j', 't', 'e', 'w', 'p', 't', 'w', 'l', '7447', '1877', '7747', 'k', 'b', 'x', '8565', 'q', '8575', '5711', '2949', '5637', '2197', '4905']

A: b, e, j, k, l, p, q, t, w, x
****
Q: ['b', '2705', 'o', '5743', 'y', '2799', 'u', '4357', '4489', '4259', 'f', 'r', 'p', 'm', '1869', '4971', '1317', '3297', '3409', '3481', '3795', 'n', '3079', 'a', 'm', 'p', 'x', 'm', '6465', '581', 'r', 'w', '9617', '4875', 'r', 'l', '8333', '7997']

A:
a, b, f, l, m, n, o, p, r, u, w, x, y
****