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: ['j', '8929', '3801', '8439', '4373', '7765', '7399', 'm', '3715', '6373']

j, m