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:
['1931', 'c', 's', '8767', 'z', '8977', '9249', '365', 'p', '7187', 'p', '961', 'k', 'k', '423', '5999', '4697', '6251', '6441', '1821', 's', 's', 'f', '5365', 'z', '5113', 'y', 'k', 'i', '5627', 'u', 'w', '4103', '8035', '7105', 'o', 'n', 's', 'y']
answer:
c, f, i, k, n, o, p, s, u, w, y, z


question:
['d', 'o', '7643', '9065']
answer:
d, o


question:
['r', '8751', '3385', '7299', '5657', 'w', '1013', 'n', 'k', 'k']
answer:

k, n, r, w