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:
['5971', 'x', 'c']
answer:
c, x


question:
['6027', 'v', 'b', 'l', '7853', 'r', 'y', '2919', '3831']
answer:
b, l, r, v, y


question:
['r', 's', 'a', '3755', 'i', '4211', '3465']
answer:

a, i, r, s