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:
['7055', '2573', '1713', 'x', 'm']
answer:
m, x


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:
['n', 'a', '4285', 'p', '9531', '4003', 's', '6801', '8353', '2779']
answer:

a, n, p, s