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:
['a', '7599', 'i', '9455', '3955', '2015', 'j', '7345', 'x', 't', 'c', '1317', '9155', '6383', '7793', 'n', '5581', 'v', '3485', 'n', 'r']
answer:
a, c, i, j, n, r, t, v, x


question:
['5737', 'b', 'e', 't', '7419', 'n', 'y', '5225', '6485', 'b', '1343']
answer:
b, e, n, t, y


question:
['n', 't', '2901', '9697', 'a', 'j', 'x', 'a', '4437', '2255', '2177', 's', '3173', 'j', 't', '5713', '4091', '4253', '5553', 'i', '4533', 'i', 'e', '6899', 's', '3541', '2139', '2705', 'm', 'u']
answer:

a, e, i, j, m, n, s, t, u, x