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: ['k', '7993', '4623', '1965', 'k', 'p', 'q', '9757', 'z', 'g', 'm']

g, k, m, p, q, z