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:
['5337', '4877', '9443', '3445', 'u', '2571', 't', 'n', 'x', '1985', '5145', '3397', 'p', '9259', 's', 'x', 'u', 'c', 'g', 't', 'j', '829', '8273', 'e', 'j', 'r', 'x', '865', '4773', 'h', '4407', '8591']
answer:
c, e, g, h, j, n, p, r, s, t, u, x


question:
['1429', '7763', '9737', 'l', '1865', 's', '9871', 'e', 'c', 'q', '2727', 'v', 'p', 'd', 'p', '6771', 'c', '7051', 'e', 'b', 'd', 'o', '7427', 'x', 'e', 'm', 'u', '4887', '1649', 'u', 'h', '5249', 'e', '7579', '8549']
answer:
b, c, d, e, h, l, m, o, p, q, s, u, v, x


question:
['1479', '4683', 'e', '9673', '8313', '4429', '9297', '3293', 'y', 'a', 'f', '4887', '6861', '8303', 's', '1081', 'f', '4719', 'f', 'v', 'x', '2561']
answer:

a, e, f, s, v, x, y