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: ['m', '6761']

SOLUTION: m

PROBLEM: ['s', '2507', '3091', 'g', '7643', '2573', 'w', 'r', '1977', 'q', 'c', 'j', '1335', '9671', '7317', '567', '2041', '5777', 'w', 'm']

SOLUTION: c, g, j, m, q, r, s, w

PROBLEM: ['n', 'l', 'n', 'w', 'a', 'd', '8977', '5671', 'j', 't']

SOLUTION:
a, d, j, l, n, t, w