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: ['6249', '1235']

SOLUTION: -1

PROBLEM: ['895', '2049', '8839', '1773', 'v', '467']

SOLUTION: v

PROBLEM: ['8535', 'x', '3915', 'f', '5043', 'y', '9395', '1623', '633', '9041', '1577', '1011', 'k', '7771', '2961', '8957', '691', '6407', '117', '2425', 'y', 'e', 'r', '6263', '1731', '7197', 'd', 'x', '1115']

SOLUTION:
d, e, f, k, r, x, y