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: ['a', 'a', 'b']

SOLUTION: a, b

PROBLEM: ['1799', '6409', '9257', '5923', 'm', 'j', '2565', '715']

SOLUTION: j, m

PROBLEM: ['v', 'v', 'c', 'p', '3153', '7027']

SOLUTION:
c, p, v