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:
['2453', 'r', 'd', '8499', 't', 's', 'h', 'a', 'm', '9271', 'g', '2599', '6209', 'o', 'i', '4069', 't', '6793', '7679', '6643', '7359', 'm', 'f', 'w', '775', '3347', '6161', '9745', 'i']
answer:
a, d, f, g, h, i, m, o, r, s, t, w


question:
['6697', 'j', '1571', '4989', 'o', '1143', 'i', '2969', '2541', '4899', 'i', '4751', 'n', 'b', '801', '4357', '3855', '49', 'm', '211', '7281', '121', '5231', '8313', '8967', '8043', '7699', 'r', '4315', '8637', '3339', '4437']
answer:
b, i, j, m, n, o, r


question:
['7791', 'f', '971', '8705', '9877', '9891', 'w', '939', '3855', 'g', 's', '8517', 'f', 's', 't', '3513', 's', 'i', 'b', '4069', 'i', '939']
answer:

b, f, g, i, s, t, w