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: ['7595', '5303', '3985', 'n', 'w', 's', 'r', 'f', '8237', 'q', 'y', 'f', '3121', '2463', '4597', 'q', '6801', 'f', 'i', '8563', '3267', 'k', '6157', 'f']

SOLUTION: f, i, k, n, q, r, s, w, y

PROBLEM: ['1931', 'c', 's', '8767', 'z', '8977', '9249', '365', 'p', '7187', 'p', '961', 'k', 'k', '423', '5999', '4697', '6251', '6441', '1821', 's', 's', 'f', '5365', 'z', '5113', 'y', 'k', 'i', '5627', 'u', 'w', '4103', '8035', '7105', 'o', 'n', 's', 'y']

SOLUTION: c, f, i, k, n, o, p, s, u, w, y, z

PROBLEM: ['r', '1075', '9607', '961', 'c', 's', '4137', 'd', 'k', '1219', '2651', '2903', 'p', '1269', 'h', 'v', '3473', 'w', '967', '6323', 'h', '997', 'p', 'p', '8519', '4897', '219', 'r', 'e', 'u', '6361', '6109', '8277', '1763', 'w', 'u', '2189', '8893', 'w', 'b', '5145', '5493', 'j']

SOLUTION:
b, c, d, e, h, j, k, p, r, s, u, v, w