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: ['b', 'n', '6721', 'q', '763', '1629', 'r', 't', '7273', '9097']

b, n, q, r, t