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: ['p', '5229', '7521', 'y', 'n', 'u', 'c', '4047', '781', 'a', '4707', '7149', 'j', 'm', 't', '515', '7691', 'h', '4879', 'j', '6593', 'n', 'p', '2949', '1343', 'y', '2629', 'p', 'b', 'b', '2861', 'a']

Answer: a, b, c, h, j, m, n, p, t, u, y


Question: ['4925', 'i', 'q', 'k', '7615', 'r', '7217', 'o', '8097', '9151']

Answer: i, k, o, q, r


Question: ['8635', 'u', '919', '2363', 'l', '951', '4081', '487', 'p', '5695', '1261', 'r']

Answer:
l, p, r, u