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: ['q', 'g', 's', 'g', 'z', '987', '777']

SOLUTION: g, q, s, z

PROBLEM: ['5159', '6407', '4021', '6655', 'c', 'k', 'w', '7191', 'l', '4321', '1609', 'm', '1991', '9261', '511', 'p', '7495', 'b', 'e', '4647', '2711', 'd', 'y', '3835', '5037', '3613', '2695', '3367', 'm', 'j', 'y', '9561', '4889', 'a', 'z', '2253', 'p', 't', 's', '8371', '2859', 's']

SOLUTION: a, b, c, d, e, j, k, l, m, p, s, t, w, y, z

PROBLEM: ['s', 'o', 'b', '2127', 't', '5225', 'x', '8253', 'w', 'q', 'g', '5191', '9567', 't', '4445', '7321', '8621', '9165', 'j', '4039', 'z', 'k', '2801', 'w', 'k', 'o', 'c', 'w']

SOLUTION:
b, c, g, j, k, o, q, s, t, w, x, z