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:
['7301', '7999', 'x', 'r', '6881', 'e', '609', 's', '7495', 'a', 's', '1961', 'q', 'x', '373', '6289', '4847', '5969', 't', '5487', '7639', '9039', '2395', 'b', 'd', '1447', 's', '8137', 's', '443', 'f', 'z', '4823', 'k', 'i', 'o', '4739', 'w', 'f', '8853', 'a']
answer:
a, b, d, e, f, i, k, o, q, r, s, t, w, x, z


question:
['r', '9489', 'e', 'n', '6323', 'd', '3163', '265', '8587', '7891']
answer:
d, e, n, r


question:
['l', '8793', 'x', 'f', 'l', 'q', '6095', '2243', '5227', 'j', 'x', '5441', 'p', 'u', 's', 'd', 'n', 'a', '8745', 'y', '1153']
answer:

a, d, f, j, l, n, p, q, s, u, x, y