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:
['3395', '7471', 'n', '9537', '1255', '1997', '3085', '4863', '9797', '4275', 'k', 'f', '8973', '3939', 'p', 'q', '4977', '6231', '8745']
answer:
f, k, n, p, q


question:
['7595', '5303', '3985', 'n', 'w', 's', 'r', 'f', '8237', 'q', 'y', 'f', '3121', '2463', '4597', 'q', '6801', 'f', 'i', '8563', '3267', 'k', '6157', 'f']
answer:
f, i, k, n, q, r, s, w, y


question:
['e', 'n', 'g', 'q', 'h', 'j', '583', '4993', 't', '8713', '317', '7613', 'm', 'v', '7151', '979', '8729', 'u']
answer:

e, g, h, j, m, n, q, t, u, v