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.
--------
Question: ['m', '6761']

Answer: m


Question: ['e', 'z', '5199', 'x']

Answer: e, x, z


Question: ['y', 'c', 'g', '8481', '1131', '1815', '4639', '401']

Answer:
c, g, y