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: ['s', '5175', 'd', '4447', '7513', 'u', 'w', 'k', '1267', '7129']

d, k, s, u, w