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:
['v', '2989', 'z', '7843', 'e', '9923', 'y', 'b', '7611', 'u', 'u', '6227', '3145', 'w', '6451', 'g', '3129', 'o', 'r', 'z', '8349', 'u', 'h', 'd', 'g', 'a']
answer:
a, b, d, e, g, h, o, r, u, v, w, y, z


question:
['w', '491', 'x', 'u', 'z', 'q', '5411', '7629', '8261', '8629', '1441', '5139', 's', 'm', '6463', 'u', 'z']
answer:
m, q, s, u, w, x, z


question:
['3975', 'a', '8115', '7691', '7239', 'y', 'g', '5967', '119', '4937', 'p', '323', '6735', '3539', '677', 'l', '8833', '7781', 'e', '4815', 'u', '7233', '2181', 'b', 'c', 't', '3125', 'z', 'w', '5997', '6121', 'k', 'z', '2957', '8787', '4217', '385', '8653', 'd', '4787', '5901', 'i']
answer:

a, b, c, d, e, g, i, k, l, p, t, u, w, y, z