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: ['u', 'o', 'b', 'b', '5873', 'w', 'v', '4171', '7957', '3501', '2563', 'l', 'q']

SOLUTION: b, l, o, q, u, v, w

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

SOLUTION: c, y

PROBLEM: ['u', 'n', '6435', '8503', '4933', '1679', '6091', '979', '689', 't', 'j', 'e', 'a', 'z', 'i', '6047', 'x', '6497', '5447', '2445', 'k', '1371', '6485', '8679', 'u', 'n', '8687', '9599', 'w', '9519', '4823', 'n']

SOLUTION:
a, e, i, j, k, n, t, u, w, x, z