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:
['m', '6443', 'd', 'o', 'p', 'q', '3765', 'k', 'm', 'y', 'j', '3531', 'y', 't', '671', 'j', '3699', 'a', 'i', '1843', 't', 'd', '1205', 'k', 'h', '1209', '2913', '1301', 'k', 'd', '1769', '7985', 's', 'p', 'f', '4583']
answer:
a, d, f, h, i, j, k, m, o, p, q, s, t, y


question:
['p', '5229', '7521', 'y', 'n', 'u', 'c', '4047', '781', 'a', '4707', '7149', 'j', 'm', 't', '515', '7691', 'h', '4879', 'j', '6593', 'n', 'p', '2949', '1343', 'y', '2629', 'p', 'b', 'b', '2861', 'a']
answer:
a, b, c, h, j, m, n, p, t, u, y


question:
['2987', 'c', '57', 'n', '8649', 'n', '6999', 'q', 'g', 'h', '8501', 'f', '1247', '1281', 'u', 'e', '3795', '5555', '8853', 'r', 's', 'f', 'a', '4823', 'k', '6859', 'n', 'i', 'n']
answer:

a, c, e, f, g, h, i, k, n, q, r, s, u