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:
['6575', '2057', '2135', '6259', '7741', '4919', '7461', 'v', '401', 'h', 'u', '2391', '2181', 'y', '9273', 'd', 'b', 's', '7993', '9323', 'b', '7015']
answer:
b, d, h, s, u, v, y


question:
['e', 'n', 'y', 'f', 'l', 'h', '455', 'y', '591', 'm', '9041', 'b', 'b', 'o', '4215', '5009', 'o', 'a', '4369', 'u', '6911', '4825', 't', 'k', '6063', '2939']
answer:
a, b, e, f, h, k, l, m, n, o, t, u, y


question:
['5627', 'j', 'u', '4263', 'h', 'r', '6923', '3219', 'w', '9861', 'x', 'r', '2739', 'c', 'f', 'g', 'v', '5365', 'j', '109', 's', '1303', '7285', '5837']
answer:

c, f, g, h, j, r, s, u, v, w, x