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: ['u', 'd', '4193', '5687', 'p', 'r', '7787', 't']

SOLUTION: d, p, r, t, u

PROBLEM: ['8821', '9833', 'l']

SOLUTION: l

PROBLEM: ['l', 's', '8453', '2211']

SOLUTION:
l, s