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: ['y', 'b', 'r', 'f', '3745', 'n', '2921', '8133', 'r']

SOLUTION: b, f, n, r, y

PROBLEM: ['7123', 'm', 'h', '4065', 'c', 'n', '187', '3899', 'r', 'k', '2071', '9481', '6277']

SOLUTION: c, h, k, m, n, r

PROBLEM: ['k', 'q', 'c', 'j', '1807', '911', '741', 'b', '9455', '4181', '8409', '9235', '9593', '3303', '131', 'q', '6165', 'x', 'l', 'e', '9787', 'f', '3249', '4739', 'e', '6583', 'u', '6875', '5871', '4647', '1097', 'd', '2667']

SOLUTION:
b, c, d, e, f, j, k, l, q, u, x