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: ['g', 'v', 'a', 'y', 'q', '2121', 'p', '4509', '819', 'i']

a, g, i, p, q, v, y