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: ['w', '743', '5757', '8731', 'k', 'p', '317', 'n', 'x', '5649', 'l', 'm', 'c', '2499', 'l']

SOLUTION: c, k, l, m, n, p, w, x

PROBLEM: ['5075', '9169', '4659', '7605']

SOLUTION: -1

PROBLEM: ['f', '225', 'z', '8417', 'v', 'd', 'y', 'a', 'k', 'q', 'k', 'n', '1009', 'i', '697', 'u', '9693']

SOLUTION:
a, d, f, i, k, n, q, u, v, y, z