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:
['459', '1729', 'b', 'c', '9619', '4461', '4347', '6733', 'i', '3631', 's', 'j', 'i', 'r', '5293', 'q', '7397', '4309', 'c', 'n', 'k', '197', 'q', '8139']
answer:
b, c, i, j, k, n, q, r, s


question:
['p', '6123', '6961', 't', 'p', 'h', '9035', 'r', '6341', 'x', '3635', '5885', 't', '3543', '9567', '1787', 'o', '2991', 'k', '3441', '4091', 'a', 'r', '423', '9383', '7147', 'h', '663', 'd']
answer:
a, d, h, k, o, p, r, t, x


question:
['1389', 'w', 'c', 'l', '6471', '5163', '3035', '2265', 'w', 'd', '5809', 's', '6917', 'x', '3683', 'u', '7811', '3271', 'p', 'y', 'w', 'd', '2327', 'k', '9459', '4021', '5683', 'f', 'i', '937', 'l', 'p', '1993', '1113', '6239', '6171', '3779', 'z', 'n', 'y', 'l', '8593', '7639', '4929']
answer:

c, d, f, i, k, l, n, p, s, u, w, x, y, z