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: ['s', 'w', '8949', '4025']

SOLUTION: s, w

PROBLEM: ['9923', 'x', '1901', 'v', '1459', '7503', '3829', '4929', 'k', 'c', '3329', '8793', 'n', 'a', '7249', 'b', 'l', 'l', 'm', 'p', 'b', 'a']

SOLUTION: a, b, c, k, l, m, n, p, v, x

PROBLEM: ['p', 'i', '7229', '6639', '2755', 'w', 'i', '8955']

SOLUTION:
i, p, w