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:
['s', 'w', 'c', '4137', 't', '2437', '349', 'h', '4539', 't', 'b', 'y', 'q', 't', '9087', 'c', '9489', '6285', '6247', '8353', 'n', 't', '8661', 'p', 'z', 'p', '773', 'w', 'q', '8081', 'r', 'u', 'z', 'k', 'a', 'b', '7513', '5549', '5325', '1101', 's', '6507', '3317']
answer:
a, b, c, h, k, n, p, q, r, s, t, u, w, y, z


question:
['6769', '1057', '1021', 'n', '8231', '9173', '8123', 'a', '6053', 'q', 'y', '883', 'r', '1215', 'x', 'o', '9531']
answer:
a, n, o, q, r, x, y


question:
['1819', '3579']
answer:

-1