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', '6421', 'w', 'x', '669', 'h', '3853', '6609', 'p', '947', 'g', 'c', 'x', '2617', 'v', 'e', '4795', '5755', 'a', '2379', 'y', '5939', 'l', 'h', 'g', '3779', 'c', 'm', '3157', '4027', 'g', '2917', '9461', '7271', 't', 'i', '9807', '147']

SOLUTION: a, c, e, g, h, i, l, m, p, q, t, v, w, x, y

PROBLEM: ['7911', '7175', 'y', '9173', 'y', '2529', '831', 'k', '7197', 'j', '2343', 'i', 'b', '6799', '5987', '7277', 'n', 'x', 'h', '7209', 'l', 'd', 'm', 'e', '2277', '8909', 'x', '5361']

SOLUTION: b, d, e, h, i, j, k, l, m, n, x, y

PROBLEM: ['y', 'g', 'g', '2647', '5241', 'o', 'v', 'g', 'x', '4857', 'b', '783', '1259', '7783', 'n', 'n', 'k', 'd', 'p']

SOLUTION:
b, d, g, k, n, o, p, v, x, y