TASK DEFINITION: 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.
PROBLEM: ['9947', '3353', '8643', '4621', '4857', 'y', '7075', 'c', '8911']

SOLUTION: c, y

PROBLEM: ['3411', 'a', 'v', 'j', '8925', '909', 'h', 'l', 'r', '1371', 'u', '7789', '4813', 'u', 'q', 'i', '8473', 'n', '7191', 'c', '4641', 'e', '5107', 'q', 'z', 't', '105', 'q']

SOLUTION: a, c, e, h, i, j, l, n, q, r, t, u, v, z

PROBLEM: ['l', '945', 'n', '7529', '4389', '8729', '8459', '5025', '4767', '6697', '4321', 'g', '4887', 'n', '5877', '2827', '3029', 'h', 'r', '6993', '5289', 'd', '8019', '835', 's', '8349', 'a', 'p', '3275', 'k', 'l', 'n', 'a', '5939', 'b', 'f', '2009', 'q', '1773', 'z', 'c', '6747', '3055']

SOLUTION:
a, b, c, d, f, g, h, k, l, n, p, q, r, s, z