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:
['w', '1367', '5389', '9515']
answer:
w


question:
['8829', 'm', '5369', 'q', '5737', '7799', '5705', 'p', 'w', '1983', '4849', 'h', '6771', 'p', 'y', '1071', 'u', '6401', '7723', 'p']
answer:
h, m, p, q, u, w, y


question:
['o', '9103', 'b', '1021', '7441', 's', '1055', 'f', 'f', 'l', 'l', 'f']
answer:

b, f, l, o, s