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: ['f', 'p', 'n', '839', '9229', 'r', '7661', 'c', '4383', 'u', 'k', '5321', '3181', '1785', 'w', 'k', '8721', '7855', '4093', '6495', 'q', '2467', 'g']

SOLUTION: c, f, g, k, n, p, q, r, u, w

PROBLEM: ['6463', '871', '5781', '283', '9653', 'f', '9661', '3365', '2889', '5499']

SOLUTION: f

PROBLEM: ['w', 'p', '6691', '4013', '697', 'j', '5595', '5133', '6133', 'z', 'n', 'p', '1555']

SOLUTION:
j, n, p, w, z