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: ['t', 's', '1515', '223', '4353', '1077', '3155', 'x', 'u']

s, t, u, x