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: ['i', '1129', 'f']

SOLUTION: f, i

PROBLEM: ['7187', '7081', 'j', 'i', '3725', '6333', 'h', 'f', '6639', 'r', 'n', '3559', '2785']

SOLUTION: f, h, i, j, n, r

PROBLEM: ['k', '3199', '6467', 'k', '2167']

SOLUTION:
k