You will be given a definition of a task first, then some input 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.

['7271', '2059', 'l', '1541', '1057', 's', 'w', 's', '8523', 'p', '4505', 'p', 'b', '859', '4093', '3711', '715', 'v', '5349', 'g']
Output:
b, g, l, p, s, v, w