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:
['j', '425', '6223', '6631', 'y', '7649', 'r', 'a', '7933', '7947', 'l', 'l', '8755', 'g', 'b', '3351', '49', 'v', 'm', 'x', '3291', '1007', '1401', 'z', 'q', 'a']
answer:
a, b, g, j, l, m, q, r, v, x, y, z


question:
['6709', 't', 'n', 'k', '991', 'a', '8899', '3563', '527', 'm', '4599', '6679', 'm', 'x', 'f', 'o', '3275', 'x', '677', 'b', '3329', '3593', '5183', '5753', 'u', '6045', '2607', 'y', '9873']
answer:
a, b, f, k, m, n, o, t, u, x, y


question:
['r', '67', '1353', 'p', '2103', '3443', 'c', '9229', '4085', '8765', '5791', '3699', '6207', 'n', 'x', 'g', 'b', 'y', '811', '8879', 'g', '1391', 'j', 'j', 'f', '7473', '9025', 'm', '7467', '9427', '4355', 'e', 'h']
answer:

b, c, e, f, g, h, j, m, n, p, r, x, y