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: ['d', 'p', 'k', '9679', 'x', 'j', '7481', '1815', 't', 'w', '6513', 'j', '5079', '5219', 'p', '9545', 'a', '1931', '9973', '8125', '5169', '2791', 't', 'd', '2057', 'e', 'x', 'y', '7409', 'u']

SOLUTION: a, d, e, j, k, p, t, u, w, x, y

PROBLEM: ['w', 'g', '1649', 'a', '2115', '6763', 'r', 't', 'l', 's', 'y', '5659', 'a', 'b']

SOLUTION: a, b, g, l, r, s, t, w, y

PROBLEM: ['l', '6159', 'h', '9595', '7541', 'h', 'e', 'j', '3821', '9355', 'i', '407', '2791', '8567', 'g', '4227', 'c', '9211', '7821', 'j', '7641', '7335', 'b', '687', 'z', 'e', '7217', 'c', '3115', '9997', 'r', 'l', 'h', 'u', 'n', 'm', 'w', 'm', '7781', '5657', 'c', 'q']

SOLUTION:
b, c, e, g, h, i, j, l, m, n, q, r, u, w, z