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:
['9025', '3259', '4863', 'u', '6443', '9931', '627', 'x']
answer:
u, x


question:
['749', 'r', 'a', 's', 't', '5905', 'm', 'd', '8437', '4583']
answer:
a, d, m, r, s, t


question:
['9101', '891', '4145', 'e', 'p', '8479', 'd', 'e', 'i', 'i', '875', '5373', '5915', '1469', 'r', 'h', 'v', 'u', '7957', '6521', '9939', '3609', '1013', 'b', '891', 'v', '5269', 'c', '5805', 'w', '9827', '4569', 'g', '5539', 's', 'r', 'k', '1007', 'w', 'j', 'a', '8663', '8111', '6575', '9149']
answer:

a, b, c, d, e, g, h, i, j, k, p, r, s, u, v, w