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:
['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:
['l', '6313', '3199', 'w', '249', '8747', '7391', '3871', '173', 'x', 'o', '8647', '4413', '3645', '6123', '701', 'q', '2147', '4289', '7333', '533']
answer:
l, o, q, w, x


question:
['m', 'f', 'j', 'i', '1557', '2849', 'm', '2531', '6845', '6765', '9211', 'q', 'p', 'x', 'h', '237', 'r', '4041', '6871', 'q', '2715']
answer:

f, h, i, j, m, p, q, r, x