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.

['s', 'u']
s, u

['4041', 'l', 'g', '9571', '9295', '1395', 'l', 'p', 'f', 'w', 'g', '1721', '2421', 'w', 'z', '2235', 'p', '7851']
f, g, l, p, w, z

['4789', '3375', 'j', '2243', 'g', 'h', '5623', 'k', 'x', '769', '7811', 'n', 'j', '695', 'y', 'f', 'p', 'u', '3413', 'a', 'm', '141', 'b', '1247', 'u', '7355', '4167', '3471', '135', 'i', 'j', '8097', 'f', '1235', 'x', 'r', '7343']

a, b, f, g, h, i, j, k, m, n, p, r, u, x, y