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:
['o', 'l', 'm', 't', '4487', '1019', '9903', 'c']
answer:
c, l, m, o, t


question:
['4641', '2881', 'c', '4827']
answer:
c


question:
['4125', '1327', '6557', '5707', '7895', '1185', 'e', '7099', 'g', 'n', 'w', '3531', '2239', 's', 'c', 'o', 'o', 'd', 'a', 'a', 'q', '3561', 'h', 'n', 'f', 'd', '1935', 'p', 'p']
answer:

a, c, d, e, f, g, h, n, o, p, q, s, w