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:
['749', 'r', 'a', 's', 't', '5905', 'm', 'd', '8437', '4583']
answer:
a, d, m, r, s, t


question:
['q', '9033', 'p', 'z', '1743', '247', '967', '445', '9849', 'f', '9113', 'b', 'g', '6041', 'j', '927', 'i', 'p', '6821', 'q', '6701', 'f', 'j', 'o', 'y', 'c', '7981', 'b']
answer:
b, c, f, g, i, j, o, p, q, y, z


question:
['1129', '2393', '4581', 'o', 'k', '7905', '383', 'd', 'd', 'y', 'l', 'o', 'h', '1047', '3401', '5677', '935', 'c', 'y', 'u', 'd', 'z', 'b', '4779', 'e', '4393']
answer:

b, c, d, e, h, k, l, o, u, y, z