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: ['2409', 'q', 'w', 'e', 'x', '4737', 'w']

SOLUTION: e, q, w, x

PROBLEM: ['p', 'p', '7899', 'u', '971', '7289', 't', '5217', 'k', 'z', 'y', 'y', '6905', '9499', '4085', 'x', '955', 'v', 'j', '9049', '7927', '1757', '193', '2181']

SOLUTION: j, k, p, t, u, v, x, y, z

PROBLEM: ['h', '809', 'a', 's', '173', 'z', 'k', 'c', 'o', 'p', '8971', 'u', '6645', 'q', '5325', '7275', 'x', 'h', 'x', 'x', '2137', 'b', '9915', 'e', 'f', '9309', 'y', 'o', 'g', 'n', 'u', 't', '3191', 'z', '3711', '8925', 'c', 'c', 'e', 'y', '6533', 'c', '1713']

SOLUTION:
a, b, c, e, f, g, h, k, n, o, p, q, s, t, u, x, y, z