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: ['a', 'a', 'b']

Answer: a, b


Question: ['m', 'b', 'x', 'u', 'b', 'f', '7507', '8177', '3205', '6841', 'f', '5297', 'j', 'h', '2403', '3121', '4219', '1123', 'o', 'm', 'i', '2827', 'k', 'b', '9391', 'v', '201', '6469', '1231', 'd', 'x', 'd', 't', 'w']

Answer:
b, d, f, h, i, j, k, m, o, t, u, v, w, x