You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
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.

['8129', 'a', '4245', 'y', 'm', 'a']
Solution: a, m, y
Why? Here, the unique alphabets in the list are 'a', 'y', and 'm', hence their sorted order is 'a, m, y'.

New input: ['7039', '2093', '7603', 'l']
Solution:
l