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: ['4041', 'l', 'g', '9571', '9295', '1395', 'l', 'p', 'f', 'w', 'g', '1721', '2421', 'w', 'z', '2235', 'p', '7851']

SOLUTION: f, g, l, p, w, z

PROBLEM: ['p', 'f', 'h', '1977', '6221', 'i', 'a', 'l', '5225', '8059', 'c', 'w']

SOLUTION: a, c, f, h, i, l, p, w

PROBLEM: ['n', 'f', '7375', '343', 'm', 's', '4455', '9901', '9315', '6357', 'k', '8011', '2323', 'y', '5531', '8151', '2857', '3977', 'j', 'w', 'n', '7041', 'k', '3917', '677', '8821']

SOLUTION:
f, j, k, m, n, s, w, y