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: ['h', 'l', 'i', '1507', 'h', '409', '6777', 'u', '5563', '6113', '6513', '9949', '461', 'z', 'm', '2519', 'r', '4699', 'n', 'x', '4645']

SOLUTION: h, i, l, m, n, r, u, x, z

PROBLEM: ['6575', '2057', '2135', '6259', '7741', '4919', '7461', 'v', '401', 'h', 'u', '2391', '2181', 'y', '9273', 'd', 'b', 's', '7993', '9323', 'b', '7015']

SOLUTION: b, d, h, s, u, v, y

PROBLEM: ['9061', '6207', 'b', 'q', 'l', '265', 'a', '6405', '9715', 'm', '3795', 'n', '9797', 'j', 'k', '5647']

SOLUTION:
a, b, j, k, l, m, n, q