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:
['7911', '7175', 'y', '9173', 'y', '2529', '831', 'k', '7197', 'j', '2343', 'i', 'b', '6799', '5987', '7277', 'n', 'x', 'h', '7209', 'l', 'd', 'm', 'e', '2277', '8909', 'x', '5361']
answer:
b, d, e, h, i, j, k, l, m, n, x, y


question:
['9635', 'g', 's', '2665', '4647', 'q', '6887', '7943', 'g', 'k', 'n', '7063', '3077', '2691', '6781']
answer:

g, k, n, q, s