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.

['1971', 'g', 't', 't', 'x', 'q', 'o', 'm', 'h', '9481', '1729', '5527', 'u', '3157', 's', '8795', 'z', 'g', 'i', '1649', 'p', '65', 's', 'u', '6843', 'r', 'l', 'k', 'n', 's', 'm', '7991', 'u', 'a']
a, g, h, i, k, l, m, n, o, p, q, r, s, t, u, x, z

['8829', 'm', '5369', 'q', '5737', '7799', '5705', 'p', 'w', '1983', '4849', 'h', '6771', 'p', 'y', '1071', 'u', '6401', '7723', 'p']
h, m, p, q, u, w, y

['s', 'x', 'j', 'x', '8445', '4643', '4719', '5981', '8261', '7459', '4259', 'b', '9363', 'b', 'k', '9593', 'c', '6975', '7629']

b, c, j, k, s, x