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:
['8315', 'b', '4333', 'f', '6507', '6211', '3475', 'c', 'e', '8039', '661']
answer:
b, c, e, f


question:
['o', 'l', 'm', 't', '4487', '1019', '9903', 'c']
answer:
c, l, m, o, t


question:
['7615', '5375', '6839', 'x', '6955', 'x', '2613', 'l', 'n', '8481', '3471', '6169', '6977', 'r', '377', 'd', '2383', '6809', '2601', 'j', 'a', 'g', 'u', '83', 'c', 'y', '7763', 'r', 'o', 'p', '6107', '5169', '7293', 'a', 'd', '2051', 't', 'x', '4373', 'e', 's', '1389']
answer:

a, c, d, e, g, j, l, n, o, p, r, s, t, u, x, y