Definition: 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.
Input: ['4663', '6515', 'z', 'r', '3075', 'b', 'h', '8131', '6735']

b, h, r, z