Definition: 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.
Input: ['o', '9103', 'b', '1021', '7441', 's', '1055', 'f', 'f', 'l', 'l', 'f']

b, f, l, o, s