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:
['8879', 'x', '1383', '4925', '2867', 'j', 't', 'e', 'w', 'p', 't', 'w', 'l', '7447', '1877', '7747', 'k', 'b', 'x', '8565', 'q', '8575', '5711', '2949', '5637', '2197', '4905']
answer:
b, e, j, k, l, p, q, t, w, x


question:
['4299', 'b', '4171', '7639', '6609', '927', '5249', 'o', 'p', '9851', 'e', '1311', '3777', '7799', '7687', '8809', 'c', 'r', '47', '1925', '1847', 'r', 'd', 'r', '1871', '5935', 'r', '2283', 'p', 'p', '2727', 'c', 'i', '7357', 'y', '5103', '6115', 'q', 'w', 'u', '9201', '4221', '7717', 'o']
answer:
b, c, d, e, i, o, p, q, r, u, w, y


question:
['7147', 'd', 'y', 'y', 'n', 's', '4763', 'j', 'b', 's', '4039', '9151', '6763', 'w', 'g', 'k', 'j', 'x', 'h', 'm', '3805', 'i', '5393', 'n', 'w', 'a', '1121', 'i', 'e', '4877', '3407', 'i', 'm', '3389', '3983', 'f', '8075', 'g', '6641', '17']
answer:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
a, b, d, e, f, g, h, i, j, k, m, n, s, w, x, y


