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', '8797', 'i', '5443', 'i', 'f', '7593', 'u', 'h', '3251', 'l', '681', 'y', 'n', 'r', '1699', '1379', '8987', '6955', 'x', 'p', 'x', '553', 'q', '5679', 'q', 'w', '9007', 'r', '8945', '7351', 'a', 'v', 'k', '1309', 'v', 'i', '4161', 'a', 'q', '2919', '6917', '6845']
answer:
a, f, h, i, j, k, l, n, p, q, r, u, v, w, x, y


question:
['1979', 'b', 't', '1101', '7953', '2451', '7539', '6833', 'u', '49']
answer:
b, t, u


question:
['1029', 'j', 'x', '4655', 'k', 'u']
answer:

j, k, u, x