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:
['3947', '4809', 'b', 'a', '4769', '4179', '535', '5965', 'f', 'j', '2265', 'w', '3103', 'u']
answer:
a, b, f, j, u, w


question:
['j', 'r', 'z', 'f', '1485', '2419', 't', 'd', '6023']
answer:
d, f, j, r, t, z


question:
['4503', 'q', 'd', '9231', '4297', '3097', 'c', 'a', '9687', 'f', '559', 'l', '7297', '3579', '2083', 'a', '9763', '4837', '8373', 'd', 'e', 'k', 'w', 'f', 'a', 'p', 'x', 'p', '3929']
answer:

a, c, d, e, f, k, l, p, q, w, x