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:
['887', 'p', '3819', '2727', '1407', 'b', 'n', '737', 'd', 'w', 'q', '6877']
answer:
b, d, n, p, q, w


question:
['u', '635', '5249', '9457', 's', '9317', '9407', 'l', 'w', '9705', 'k', '429', '5489', 'e', 'd', '2457', 'o', '4665', '1675', 'l', 'y', 's', 'o', 't', '4285']
answer:
d, e, k, l, o, s, t, u, w, y


question:
['4039', 'p', 'h', '8621', 'o', '6641', 'e', '845', 'q', '4217', '7313', '6105', 'o', 'l', '3581', 'v', '613', 'w', '6463', 'p', '1815', '6741', '7373', 'e', 'r', 'f']
answer:

e, f, h, l, o, p, q, r, v, w