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:
['g', '6867', '7965', '3313', 'k', '1827', '7337', 'u', '1209', '5145', 'w', 'h', '9059', 'u', 'b', '3189', '2837', 'k', 'y', 'e', 'b', '4479', '541', '7103', 'h', 'm', '2177', '6377', '3993', '7167', 'q', '2145', '5007', '9135', '5331', 'e']
answer:
b, e, g, h, k, m, q, u, w, y


question:
['k', '6103', '6553', 'x', 't', '4367', 'z', 'v', 'p', 'g', 'l', '9673', 'c', '7481', '9823', '3265', 'd', 'o', 'x', '239', '1283', '9241', 'v', '7617', 'o', '7559', '1151', '2931']
answer:

c, d, g, k, l, o, p, t, v, x, z