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:
['w', 'n', '729', '2491', 'n', 'x', '915', '1869', 'z', '8491', '9947', '561', '829', 'n', 't', 'i']
answer:
i, n, t, w, x, z


question:
['z', 'h', '2065', '6773', 'v', '151', '8957', 't', 'l', 'j', '7867', 'v', '799', '9009', '4317', 'm', '6921', 'r', '1245', '5637', 'x', '4465', 'f', 'y', '3549', 'e', 'f', 'm', 't', '6281', '4241', '3415', 'z', 'g']
answer:
e, f, g, h, j, l, m, r, t, v, x, y, z


question:
['4871', 'q', '8603', 'c', '2583', '2965', 'b', 'b', 'o', '7507']
answer:

b, c, o, q