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: ['t', 't', 'p', '3245', 'x', 'g', 'i', 'u', '2599', '8613', 't', 'v', 'p', '5635', 'y', '9567', '5193', '8617', 'q', 'f']

SOLUTION: f, g, i, p, q, t, u, v, x, y

PROBLEM: ['a', '2579', 'f', '6787', '123', '225', '6499', '4419', 'o', '1785', '7981', 'z', 'b', '2441', '2821', 'o', 'k', '2747', 's', 'u', 'q', '3901', '7629', 'k', 'm', 'q', '6577']

SOLUTION: a, b, f, k, m, o, q, s, u, z

PROBLEM: ['2455', '6471', '3625', 'b', '5981', '9389', 's', '3727', 'a', '4695', 'n', '411', 'a', 'e', '5283', '9773', '6819', '5367', 'm', 'b', 'y', 'z', 'c', 'l', 'd', '8555']

SOLUTION:
a, b, c, d, e, l, m, n, s, y, z