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:
['q', 'g', 's', 'g', 'z', '987', '777']
answer:
g, q, s, z


question:
['933', 'd', '5067', '3189', '4695', 'u', 'x', '1517', 'z', '7935', 'i', 'd', 'l', 'x', '7139', 'z', '2685', '3297', 'x', 'u', '2131', '3065', 'v', '3571', 'r', '3077', '5707', '6707', '4447', 'x', 'k', 'v', '3525', '5171', 'm', '1109']
answer:

d, i, k, l, m, r, u, v, x, z