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:
['m', '8127', '7519', '4543', '2809', '9855', 'n', '6241', 'w', 'w', 'q', 'w', 'p', '8599', '7819', '3817', 'm', 'q']
answer:
m, n, p, q, w


question:
['e', '1251', 'y', '6689', '6389', 'h', 't', '503', '5093', 'e', '923', '7051', 'm', 'u', '4501', '3289', '6887', '8341', 'o', '3671', 'n', 'w', '7749', 's', 'j', 'o', '8429', 'q', 'v', 'p', 'd', 'g', 'i', 'f']
answer:
d, e, f, g, h, i, j, m, n, o, p, q, s, t, u, v, w, y


question:
['9141', 'c', 'p', '1537', 'k', '8955', '4857', '4845', '8013', 'o', 'p', '8377', '709', 'g', 'z', 'f', '7035', '8675', '6017', 'x', '2491', 'q', 'p', 'o', '3991', 't', 'i', 'c', '2377', '5905', 'g', '6671', 'g', '4431', '3823', 'y', 'n', '6309', '7857', '2017']
answer:

c, f, g, i, k, n, o, p, q, t, x, y, z