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:
['p', '5229', '7521', 'y', 'n', 'u', 'c', '4047', '781', 'a', '4707', '7149', 'j', 'm', 't', '515', '7691', 'h', '4879', 'j', '6593', 'n', 'p', '2949', '1343', 'y', '2629', 'p', 'b', 'b', '2861', 'a']
answer:
a, b, c, h, j, m, n, p, t, u, y


question:
['5957', 'd', 'i', 'b', 'e', '5565', 'c', 'i', '2919']
answer:
b, c, d, e, i


question:
['r', 'n', '5881', '9531', 'k', '6551', 'n', '2365', '5663', 'm']
answer:

k, m, n, r