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.

['2697', 's', '8733', 'n', '5871', 'f']
f, n, s

['7013', '8755', 'u', '9377', 'n', '6997', '507', '8557', '9745', 'g', '3019', '93', 'l', '1219', 'a', '393', '2573', 'q', 'b', '6101', 'e']
a, b, e, g, l, n, q, u

['r', 'u', '3975', '6021', 'i', 'e', '4221', 'p', 'l', 'i', 'k', 'y', '2947', 'f', '9043', '4171', '8523', 'n', 'q', 'x', 'm', 'p', '2229', '23', 'r', '7671', '681', 'o', '111', 'a', '9181', 'v', '7825', 'd', '9143', 'y', 'b', '5423', 'o', '2673']

a, b, d, e, f, i, k, l, m, n, o, p, q, r, u, v, x, y