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: ['o', '9599']

Answer: o


Question: ['4009', 'y', '9077', 'p', 'q', '6711', '6443', '5491']

Answer: p, q, y


Question: ['315', '9975', '3013', 's', '6131', 'e', 'e', 'u', 'a', '1729', 'g', 't', 'y', 'f', '7523', 'e', 'g', '489', 'm', 'p', 'f', 'e', '2077', 'e', 'g', 'c', 'l', '6389', 'k', 'b']

Answer:
a, b, c, e, f, g, k, l, m, p, s, t, u, y