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:
['1449', 'a', '6261', '303', '4651', 'n', 'u', '1595']
answer:
a, n, u


question:
['8739', 'v', 'm', '6277', 'l', 's', '109', '8057', '3835', 'd', 'u', 'f', 'w', 'd', 'p', '7705', '3643', '4455', 'u', 'p', 'u', '9407', 'g', 'w', '595', 'z', '6827', '6879', 'w', 'w', '6973', 'm', 'e', '1553', 'v', '3529', '8953', '3903', '5713', '8249', 'e', '1113', 'b', 't', 'r']
answer:
b, d, e, f, g, l, m, p, r, s, t, u, v, w, z


question:
['1209', '9681', 'v', 'b', '1915', '575', 'k', '8393', 'x', '9877', 'i', 'v', 'c', '4225', '1551', 'v', '8445', '9231', 'w', '9245', '6399', 'y', 'z', '2489', 'm', 'r', '4689', 'r']
answer:

b, c, i, k, m, r, v, w, x, y, z