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:
['m', '7807', 'n', 'w', '5097', '1023', '2723', 'u', '3055', '7285', 'f', 'm', 'w', '5197', '9743', '7519', '4451', 'c', 't', '1939', '5847']
answer:
c, f, m, n, t, u, w


question:
['9273', '5219', 'e', '9413', 'v', 'h', '5657', '797', '2303', '2119', '4791', '2757', '4983', 'h', '9681', '4503', '6657', 't', 'i', 'g', '9375', '9901', 'm', 'y', '6461', 'h', '6663', '9493', '5897', '8829', 'd', 'x', '901', '833', 'u']
answer:
d, e, g, h, i, m, t, u, v, x, y


question:
['y', 'u', 'y', 'a', '5617', 'f', '4609', 'j', 'w', 'd', '4115', 'k', '4005', '4883', 'i', 't']
answer:

a, d, f, i, j, k, t, u, w, y