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: ['r', 's', '2471', 'n', '635', 'k', '3551', '7041', '8765', '1221', '8439', '7773', '6471', 'u', 'p', '2093', '6479', '1435', '6881', 'a', 'y', 'm', 'r', '1627', 'w', 'k', 'b', '3095', '9059', '285', 'y', 'a', 'm', 'x', '637', 'i', '3407', 'e', 'e']

SOLUTION: a, b, e, i, k, m, n, p, r, s, u, w, x, y

PROBLEM: ['4423', 'u', '189', '7167', 'e', 'n', '1289', 'r', '5423', '9105']

SOLUTION:
e, n, r, u