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:
['1447', 'q', '9529', '2971', 's', '7351', '6753', '3493', 'v', 'c', 'x', '3097', '9145', 'b', 'e', 'b', '2967', '6933', 'e', 's', 'v', 'f', 'z', 'r']
answer:
b, c, e, f, q, r, s, v, x, z


question:
['u', 'd', '4193', '5687', 'p', 'r', '7787', 't']
answer:
d, p, r, t, u


question:
['6439', '6843', 'p', '3777', 'c', 'b', '1063']
answer:

b, c, p