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:
['9113', '3625', 'u', '8189', '3649', '259', '5539', '1583', 'g', '4037', 'y', 'v', '8337', 'd', 'q', 'j', 'c', 'h', 'p', '1601', 'z', 'c', 'n', '1767', '1679', '1805', 'm', '4469', '2487', '6015', '973']
answer:
c, d, g, h, j, m, n, p, q, u, v, y, z


question:
['s', 'u']
answer:
s, u


question:
['o', 'b', '6993', '3471', '8725', '2877', 'y', '5137', '4533', '9413', '5131', 'n', '6841', 'i', '7725', 'd', 'q', 't', '2465', 'k', 'g', '3847', 'e', '2291', 'y', 'c', '5827', '9437', '3191', 'b', 'w', '4435', '4201', '9249', '8851', 'v', '3779', '7307', 'n', 't', '7737', 'm', 'g']
answer:

b, c, d, e, g, i, k, m, n, o, q, t, v, w, y