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: ['a', 'j', '3461', '7867', 'x', '2659', '5149', 'i', '8199', 'x', 'y', '5421', 'u']

a, i, j, u, x, y