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:
['1595', '2915', 'o', 't', 'c', 'h', '3969', '5407']
answer:
c, h, o, t


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:
['2193', 'v', 'p', 'p', '5439', '4595', '2825', 'n', 'r', '2315', 'r', 't', 'k', '4623', '6795', 'v', '8745']
answer:

k, n, p, r, t, v