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:
['n', '7489', 'n', 'n', '9787', '7829', 'n', '3481', 'v', 'l', '8927', 'c', 'm', 'd']
answer:
c, d, l, m, n, v


question:
['1233', '405', '8901', '7147', '8841', 's', 'v', '3131', 'p', 'd', 'y', '5873', '439']
answer:
d, p, s, v, y


question:
['o', 'x', '3435', 'l', '1449', 'p', '6747', 'c', 'v', 'v', 'e', 'y', 'd']
answer:

c, d, e, l, o, p, v, x, y