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: ['u', '5311', 'm', '3187', '507', 'n', '1403', 'x', 's', 'q']

m, n, q, s, u, x