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.

['8949', 'm', 'g', '7283', '2689', '4243', 'm', '9391', '8365', '871', '9307', 'v', '6103', '1449', '5779', 't']
g, m, t, v