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:
['f', 'p', 'n', '839', '9229', 'r', '7661', 'c', '4383', 'u', 'k', '5321', '3181', '1785', 'w', 'k', '8721', '7855', '4093', '6495', 'q', '2467', 'g']
answer:
c, f, g, k, n, p, q, r, u, w


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:
['z', 'x', '1839', 'q', 'l', '8963', 'q', '3251', '449', 'a', '2819', 'c', 'l', 'm', 'j', 'v', '827', '4093', '6629', 'l', '7153', '3243']
answer:

a, c, j, l, m, q, v, x, z