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:
['5737', 'b', 'e', 't', '7419', 'n', 'y', '5225', '6485', 'b', '1343']
answer:
b, e, n, t, y


question:
['h', 'l', 'i', '1507', 'h', '409', '6777', 'u', '5563', '6113', '6513', '9949', '461', 'z', 'm', '2519', 'r', '4699', 'n', 'x', '4645']
answer:
h, i, l, m, n, r, u, x, z


question:
['7467', 'a', 'x', 'p', 'r', 'y', 't', 'l', 'p', '5485', 'k', '3503', '6583', '811', '5013', 'f', 'r', 'w', 't', 'w', '1681', '1745']
answer:

a, f, k, l, p, r, t, w, x, y