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:
['o', 'm', '8015', '787', '4787', '1727', 'f', 'e', 'c']
answer:
c, e, f, m, o


question:
['5433', '4011', '2113', '2299', 'e', '9829', 'd', 'q', 'e', '3921', 'a', 'q', '8953', 'q', 'g', 'w', 'z', 'u', '4425', 'b', 'q', '5315', 'b', 'u', 'h', 'y', '9733', 'b', 'c', '1225', 'a']
answer:
a, b, c, d, e, g, h, q, u, w, y, z


question:
['k', '1515', 'y', '7709', 'p', '9689', '5243', 'e', 'y', '9269', '275', '9281', '4733', '1721', 'h', '3779', 'c', '9305', 'f', '2881', 'k', 'w', '9543', 'i', 'm', 'g', 'h', 'q', 'b', '4559', '4903', 'm', '1037', 'd', '2081', 'm']
answer:

b, c, d, e, f, g, h, i, k, m, p, q, w, y