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:
['1595', '2915', 'o', 't', 'c', 'h', '3969', '5407']
answer:
c, h, o, t


question:
['e', '8391', '7065', '6141', '3335', 't', 'i', 'c', '1791', '6333', 'b', 'z', '1621', 'e', 'h', 'u', 'o', 'q', '3195', '6507', '3253', 'c', '2067', '3917', '7111', 'r', 'j', 'd', '3987', '9139', 'm', '981', 'l', 'f', '2417', 'w', '9983', 'h', 'd', '6021', 'a', 'f']
answer:
a, b, c, d, e, f, h, i, j, l, m, o, q, r, t, u, w, z


question:
['8779', 'z', '5569', '9825', '6939', 's', 'e', 'n', 'a', 'm', '333', 'u', '3521', '3369', 'k', '7263', '7745', '5509', '6039', '663', 'z', '4727', 'n', '4509', '8215', '7181', 'e', 'w', 'b', '8607']
answer:

a, b, e, k, m, n, s, u, w, z