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: ['u', '8229', '2731', '6595', '4675', 'n', 'a', '7361', '7401', '7273', 'b', '279', '5539', '7919', 'j', 'x', '9521', '8837', '7391', 'h', 'x', 'h', '7283', 't', '3769', '2317', '9131', 'h', 'y', 'c', '1625', 'm', 'e', 'a', '8437', '7543', 'p', '2451', 'k', 'r']

SOLUTION: a, b, c, e, h, j, k, m, n, p, r, t, u, x, 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: ['4299', 'z', 'f', '9509', '1001', '7217', '4887', '2075', '7093', 'q', 'h', 's', 'b', '9729', 'x', 'f', '6701', 'i', '5837', '6445', 'e', 'b', '15', 'o']

SOLUTION:
b, e, f, h, i, o, q, s, x, z