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: ['l', 'g', 'd', 'p', '8163', '6643', 'o', 'p', 'm']

d, g, l, m, o, p