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', '491', 'x', 'u', 'z', 'q', '5411', '7629', '8261', '8629', '1441', '5139', 's', 'm', '6463', 'u', 'z']

SOLUTION: m, q, s, u, w, x, z

PROBLEM: ['i', 's']

SOLUTION: i, s

PROBLEM: ['i', 'n', '4633']

SOLUTION:
i, n

