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

Answer: a, b


Question: ['d', 'a', '6931', 'c', 'u', 'z', '9713', 'v', 'm', 'e', 'k', 'o', '9705', 'a', '5373', 'c', '2983', '8097', 'h', '3039', 'g', 'f', 'n', 'v', '853', '8227', '7573', 'j', 'h', 'k', 'o', 'k', '8897', 'd', 'g', 'd', 'd', '4039']

Answer: a, c, d, e, f, g, h, j, k, m, n, o, u, v, z


Question: ['o', '9889', 'f', '481', 'x', '1041', '7353', 'n', '7513', 'm', '9521', 'r', 'a', 'j', 'b', 'i', '4165', 'p', '1799', 'j', 'w', 'x', 'a', 'x', 'x', '4285', 'y', '355', '4349', 'k', '5821', '1419', '9845', 'y', '7731']

Answer:
a, b, f, i, j, k, m, n, o, p, r, w, x, y