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: ['6463', '871', '5781', '283', '9653', 'f', '9661', '3365', '2889', '5499']

SOLUTION: f

PROBLEM: ['g', 'p', '2925', 'n', 'o', 'y', '6381', 'l', '4963', 'g', 'm', 'u', 't', '9389', '3787', '7713', '1251', '779', 'i', 'w', '9869', 'y', 'y', '3881', 'k', 't']

SOLUTION: g, i, k, l, m, n, o, p, t, u, w, y

PROBLEM: ['9309', '5247', 'm', '9383', 'u', '2835', 'o', 'n', 't', '9989', 't', '2131', 'w', 'w', '3411', 'p', '4861', 'd', 'n', 'b', '3511', '5939', '9207', '1621', '743', '1179', '6159', '8413', '2559', '4397', 's', 'w']

SOLUTION:
b, d, m, n, o, p, s, t, u, w