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.

[Q]: ['9579', 'm', 'v', 'r']
[A]: m, r, v


[Q]: ['i', '1129', 'f']
[A]: f, i


[Q]: ['c', 'y']
[A]:
c, y