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:
['8821', '9833', 'l']
answer:
l


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:
['7969', '7117', 'g', 'a', '2079', '4769', '4497', '2671', 'x', 'j', 'p', '8285', 'c', '2309']
answer:

a, c, g, j, p, x