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:
['1799', '6409', '9257', '5923', 'm', 'j', '2565', '715']
answer:
j, m


question:
['2819', 'k', 'u', 'a', '4575', 'a', 't', 'a', 'f', '1507', '415', 'w', 'o', 'o']
answer:
a, f, k, o, t, u, w


question:
['3921', 'w', '9157', 'h', 'b', 'r', 'n', 'a', 'w', '2215', 'g', '1713', 'd', 'z', '417', 'x', 'g', '4787', '5655', '8427', 'l', '8263', 'y', 'k', '7271', 'v', '2133', 'b', 'h', 'k', 't', 'w', '9337', 'z', '753', 'v', 'f']
answer:

a, b, d, f, g, h, k, l, n, r, t, v, w, x, y, z