Detailed Instructions: 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.
Q: ['5095', '1947', 'v', 'k', '5771', '4359', 'm', 'o', '6219', 'b', 'o', 'z', '1315', '7789', '5553', '8467', '8929', '1767']
A:
b, k, m, o, v, z