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: ['w', 'i', '4383', '7667', '9617', 'y', 'a', '8051', 'w', '4857', 'y', '3953', 'u', 'o', 'y', 'i', '9201', 'g', '1807', '5367', 'g', '5263', '3995', '6665', '3113', '9433', '6315', 'm', '845', 'x', 'c', 'v', 'h', '1491', 'g', '3519', 'x', 'b', '7695']

SOLUTION: a, b, c, g, h, i, m, o, u, v, w, x, y

PROBLEM: ['n', '7489', 'n', 'n', '9787', '7829', 'n', '3481', 'v', 'l', '8927', 'c', 'm', 'd']

SOLUTION: c, d, l, m, n, v

PROBLEM: ['j', 'g', 'w', 'j', '5399', '6811', '5919', '9075', 't', '3191', '2261', 'p', '2871', 'h', '7963', '1491', 'e', 't', 'a', '9057', 'x', 'f', '2497', 'p', '1939', '6089', 'c', '1961', '867', '2851', '4647', 'i', 'p', 'z', '7117', '1949', '107', '9057', 'c', '8933', 'p', 'n', 'o', 's']

SOLUTION:
a, c, e, f, g, h, i, j, n, o, p, s, t, w, x, z