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: ['1449', 'a', '6261', '303', '4651', 'n', 'u', '1595']

SOLUTION: a, n, u

PROBLEM: ['v', 'l', 'v', '7673', '8975', 'u', '2471', '4151', '3615', '1139', 'i', 'z', '8833', 'v', '341', 'l', 'n', 'l', 'd', '9207', '1861', '3901', 'a']

SOLUTION: a, d, i, l, n, u, v, z

PROBLEM: ['4285', '2717', 'm', '4047', 'y', 'h', 'v', 'b', 'i', '6725', '7365', '511', '7455', '2425', 's']

SOLUTION:
b, h, i, m, s, v, y