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:
['o', 'v', 'w', '7939', '571', '395', '3707', 'm', 'd', 'u', 'o', 'r', '4211', '9645', '8731', '2441', 'y', '8147', '8809', 'e', 'b', '6835', 'i', '2083', 't', '3481', 'f', 'f', '5559', '3601', 'e', '5637', '5185', 't', '6777', '3419', '8637', 'p', 's', 'o', 'x']
answer:
b, d, e, f, i, m, o, p, r, s, t, u, v, w, x, y


question:
['8821', '9833', 'l']
answer:
l


question:
['2591', 'm', 'b', 'o', 'a', 'u', '3999', '339']
answer:

a, b, m, o, u