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: ['o', 'v', 'w', '7939', '571', '395', '3707', 'm', 'd', 'u', 'o', 'r', '4211', '9645', '8731', '2441', 'y', '8147', '8809', 'e', 'b', '6835', 'i', '2083', 't', '3481', 'f', 'f', '5559', '3601', 'e', '5637', '5185', 't', '6777', '3419', '8637', 'p', 's', 'o', 'x']

SOLUTION: b, d, e, f, i, m, o, p, r, s, t, u, v, w, x, y

PROBLEM: ['4993', '6641', '3127', '9409', '8453', '5909', '6109', 'y', 'f', '6859', 'c', '3863', 't', '1221', '3689', 'w', 'h', '7947', 't', '5979', 'l', 'i', '1321', '3149', 'l', 'v', '3825', 'z', '9297', 'f', 'e', '7205', 'a', 'a', '2645', '391', '4965', 'w', 'h', '7715', '9409', '3603', '4147']

SOLUTION: a, c, e, f, h, i, l, t, v, w, y, z

PROBLEM: ['4061', '7013', 'a', 'x', 'n', '6377', '5021', 'u', 'm', 't', '6973', '2211', '5187', 's', '7297', 'a', 'm', '4821', '2045', '8795', '3645', 'q', '1729', '6413', 'e', '9615']

SOLUTION:
a, e, m, n, q, s, t, u, x