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:
['d', '771', '4193', 'e', '1537', 'a', 'q']
answer:
a, d, e, q


question:
['749', 'r', 'a', 's', 't', '5905', 'm', 'd', '8437', '4583']
answer:
a, d, m, r, s, t


question:
['787', '1099', 's', 'p', '2107', 'x', 'o', 'k', '4687', 'n', 'k', '8975', '4053', 'u', '7937', '9777', 'c', '7311', '7397', '1771', 'l', 't', '4827', 'p', 'x', '9447', '8263', '8585', 'w', 'm', '2121', '6015', '7413', '3911', '5833', 'o', 'k', '2295', '8795', '303', '1807', 'q', 't', 'g', '5359']
answer:

c, g, k, l, m, n, o, p, q, s, t, u, w, x