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:
['e', 'n', 'y', 'f', 'l', 'h', '455', 'y', '591', 'm', '9041', 'b', 'b', 'o', '4215', '5009', 'o', 'a', '4369', 'u', '6911', '4825', 't', 'k', '6063', '2939']
answer:
a, b, e, f, h, k, l, m, n, o, t, u, y


question:
['5135', 'w', 'c', 'e', 't', 'r', '5337', '5645', '5935', 'x', '3489']
answer:

c, e, r, t, w, x