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.

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

['f', 'w', 'y', 't', '5269', '9989', 'p', 'v', '6609', 'v', 'c', 'q', 'm', '6565', '189', 'm', '3617', 'b', '9147', '665', 'v', '5989', '1511', '3123', '6667', '4661', '185', 'b', '3405', 'b', '6027', 'n', '6973', '505', 'g', '815', '3439', '2069', '291', 'j', 'f', '1121', '8009', 'm', '8353']
b, c, f, g, j, m, n, p, q, t, v, w, y

['3929', 'k', 'r', '1479', '7485', '5445', 'q', 'n', 'v', 'f', '495', 'x', 'f', 'p', '8927', '9039', '8085', '6759', 'w', '5929', '9605', 'p', '6979', '8129', '177', 'k', 'a', 'p', '4157', '1369', 'o', '5615', 'o', '4083', 'y', 'u']

a, f, k, n, o, p, q, r, u, v, w, x, y