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:
['9947', '3353', '8643', '4621', '4857', 'y', '7075', 'c', '8911']
answer:
c, y


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


question:
['805', '827', 'v', '3729', 'f', '2577', '4249', '9361', '9763', '247', '6089', 'b', 'g', '2565']
answer:

b, f, g, v