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', 'n', 'w', 'd', 'w', 'n', '7671', '4285', '4497']

d, n, t, w