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', 'c', '6469', 'x', '8815', '4441', '6193', 'u', 'm', 'a', '9879', 'p', '8335', 'c', 'z']
answer:
a, c, m, o, p, u, x, z


question:
['a', 'p', 'y', 'l', 'l']
answer:
a, l, p, y


question:
['t', 'z', 'x', 'n', 'j', 'j', '7615', 'z', 't', 'n', 'o', 'f', 'g']
answer:

f, g, j, n, o, t, x, z