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:
['r', 's', '2471', 'n', '635', 'k', '3551', '7041', '8765', '1221', '8439', '7773', '6471', 'u', 'p', '2093', '6479', '1435', '6881', 'a', 'y', 'm', 'r', '1627', 'w', 'k', 'b', '3095', '9059', '285', 'y', 'a', 'm', 'x', '637', 'i', '3407', 'e', 'e']
answer:
a, b, e, i, k, m, n, p, r, s, u, w, x, y


question:
['4925', '9943', '7935', '4387', '2449', '5797', 'i', '1517', 'w', 'e', '9525', 'y', 't', 'e', '2793', 'v', '9897', '8709', '7247', 'o', 'f', '5549', 'q']
answer:
e, f, i, o, q, t, v, w, y


question:
['3317', 'r', '3473', '4063', '3477', '1661', '2411', '9905', '1735', 'k', 'i', '9467', 'x', '5421', 'g', 'q', 'l', '3573', 'z', 'l', '1769', 'v', '9185', 't', '1239']
answer:

g, i, k, l, q, r, t, v, x, z