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:
['2409', 'q', 'w', 'e', 'x', '4737', 'w']
answer:
e, q, w, x


question:
['a', '533', '67', 'z', 'z', '9283', 'o', 'a', '7045', '1521', 'm', 'h', 'q', '4173', '7497', '319', '5721', '6097', 'i', '9829', '1801', '7347', 'r', 'z', '239', '4279', 'e', 'k', 'r', 'v', '6653', '599', '8597', 'd', 'r']
answer:
a, d, e, h, i, k, m, o, q, r, v, z


question:
['7941', '1687', '3307', '5673', '9709', '2659', 'k', 'n', '257', 'x', 'r', '6473']
answer:

k, n, r, x