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:
['5553', 'f', '3881', '8867', 's', 'd', 'a', '375', '7889', '3949', '2905', 'w', 'q', 'q', 'd', '4203', 'i', '2601', 'y', 'p', 'k']
answer:
a, d, f, i, k, p, q, s, w, y


question:
['r', '2271', '8317', '3987', 'h', '8585', 'y', '2723', 'u', '5357', 'v', 'j', 'p', 'k', 'z', 'k', 'c', 'r', 'y', '2961', '9471', '8359', '9923', '9089', '5771', '7381', 'j', 'q']
answer:

c, h, j, k, p, q, r, u, v, y, z