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.

['l', 'i']
i, l

['7997', 'm']
m

['1889', '4835', 'm', 'b', 't', '8085', 'w', '6929', 'v', '6119', '8107', 'b', '3827']

b, m, t, v, w