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:
['1971', 'g', 't', 't', 'x', 'q', 'o', 'm', 'h', '9481', '1729', '5527', 'u', '3157', 's', '8795', 'z', 'g', 'i', '1649', 'p', '65', 's', 'u', '6843', 'r', 'l', 'k', 'n', 's', 'm', '7991', 'u', 'a']
answer:
a, g, h, i, k, l, m, n, o, p, q, r, s, t, u, x, z


question:
['2349', 'p', 'a', '435', 'y', 'h', '3249', 'o']
answer:
a, h, o, p, y


question:
['b', '5557', 'i', 'z', '1057', 'd', '5601', 'x', '5297', 'e', '5397', 'w', '8439', '8941', '1911', 'c', '9421', 'h', 'c', '2419', 'a', 'v', 'k', 'q', 'x', '2941', 'j']
answer:

a, b, c, d, e, h, i, j, k, q, v, w, x, z