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:
['r', 'y', 'c', '3211', '9245', '8459', '8521', '5781', 'w', 's', 'd', '5299', 'a', 'y', 'g', 'm', '6435', '8605', 'e', 'h', '6871', 's', '387', 'l', '5829', 'e', 'd', '9545', '2945', 'k', 'v', 't', '8449', '2199', 'm', '2599', '1489', '6623', 'x', 'l']
answer:
a, c, d, e, g, h, k, l, m, r, s, t, v, w, x, y


question:
['6189', 'd', 'c', '5407', 'e', 't', 'y', '1095', '6533', '6197', 'h', 'j', '7723', 'm', '7181', 'u', '3035', 'y', 'n', '6259', '657', 'e', '6265', 'e', '6869', '779']
answer:

c, d, e, h, j, m, n, t, u, y