instruction:
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.
question:
['d', 'p', 'k', '9679', 'x', 'j', '7481', '1815', 't', 'w', '6513', 'j', '5079', '5219', 'p', '9545', 'a', '1931', '9973', '8125', '5169', '2791', 't', 'd', '2057', 'e', 'x', 'y', '7409', 'u']
answer:
a, d, e, j, k, p, t, u, w, x, y


question:
['9923', 'x', '1901', 'v', '1459', '7503', '3829', '4929', 'k', 'c', '3329', '8793', 'n', 'a', '7249', 'b', 'l', 'l', 'm', 'p', 'b', 'a']
answer:
a, b, c, k, l, m, n, p, v, x


question:
['o', 'q', '5157', 't', 'f', 'c', 'n', '8365', '6443', 'n', '7419', 'l', '3001', 'a', 'c', 'y', '7621', '6381', '9597', '9245', 'c', 'j', '8021', 'u', 'p', '4273', '8197', 'y', '3893', 'o', 'e', 'r', '1659', 'k', '1017', 's', 's', '1393', 'r', '2843', 'i', '6261', '5441', '9949']
answer:

a, c, e, f, i, j, k, l, n, o, p, q, r, s, t, u, y