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: ['u', '635', '5249', '9457', 's', '9317', '9407', 'l', 'w', '9705', 'k', '429', '5489', 'e', 'd', '2457', 'o', '4665', '1675', 'l', 'y', 's', 'o', 't', '4285']

SOLUTION: d, e, k, l, o, s, t, u, w, y

PROBLEM: ['q', '1111', '7523', '8865', 'p', 'v', 'y', '4375', 'f', '5451', '6157', '173', '221', '7777', 'd', 'p', '5507', '821', '8009', '2631', 'l', 'j', 'i', 'e', 'x', 'a', 'n', 'b']

SOLUTION:
a, b, d, e, f, i, j, l, n, p, q, v, x, y