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:
['6769', '1057', '1021', 'n', '8231', '9173', '8123', 'a', '6053', 'q', 'y', '883', 'r', '1215', 'x', 'o', '9531']
answer:
a, n, o, q, r, x, y


question:
['i', '9575', '8995', 'm', 'o', '3015', '4005', '6909', '7195', '3361', 'j', '5253', '9523', '8879', '5861', 'e', 'y', 'e', '1525', 'i', '807', '8469', '3333', '4017', '2237', '3387', 'o', '643', 'p', '7129', '6243', 'y', '4913', 'z', 'f', '6909', 'f', '4347', '7227', 'o', 's', '9909', '8611']
answer:
e, f, i, j, m, o, p, s, y, z


question:
['l', '6763', 'l', '3167', 'z', '3115', '1239', 'p', 'a']
answer:

a, l, p, z