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: ['w', 'i', '4383', '7667', '9617', 'y', 'a', '8051', 'w', '4857', 'y', '3953', 'u', 'o', 'y', 'i', '9201', 'g', '1807', '5367', 'g', '5263', '3995', '6665', '3113', '9433', '6315', 'm', '845', 'x', 'c', 'v', 'h', '1491', 'g', '3519', 'x', 'b', '7695']

SOLUTION: a, b, c, g, h, i, m, o, u, v, w, x, y

PROBLEM: ['3947', '4809', 'b', 'a', '4769', '4179', '535', '5965', 'f', 'j', '2265', 'w', '3103', 'u']

SOLUTION: a, b, f, j, u, w

PROBLEM: ['y', '3795', '1641', 'm', 'm', '3855', 'f', 't', 'h', 'f', '9027', '2963', '3449', 'b', '521', '6107', 'g', '9897', 'a', 'n', '7341', 'w', '7897', 'o', '6759', 'z', 'i', '8609', 'o', '4331', 'n', '6087', 'v', '7215', '577', '4871', '7863', 'q', '2557', '2753', 'z', 'y']

SOLUTION:
a, b, f, g, h, i, m, n, o, q, t, v, w, y, z