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:
['7591', '7521', 'm', '1429', 'x']
answer:
m, x


question:
['4905', 'w', '3143', '2217', '573', '1073', '63', 'a', '3971', '2887', '3485', 'y', '3893', '1059', '7623', 'x', 'd', '2991', 'e', 's', '735', 'm', 's', '257', 'x', '5559', '97', 'p', '7237', '693', '7229', 'd', '2311', '807', 'd', 'l', '1247', 'l', '359']
answer:
a, d, e, l, m, p, s, w, x, y


question:
['7271', '2059', 'l', '1541', '1057', 's', 'w', 's', '8523', 'p', '4505', 'p', 'b', '859', '4093', '3711', '715', 'v', '5349', 'g']
answer:

b, g, l, p, s, v, w