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: ['6769', '1057', '1021', 'n', '8231', '9173', '8123', 'a', '6053', 'q', 'y', '883', 'r', '1215', 'x', 'o', '9531']

SOLUTION: a, n, o, q, r, x, y

PROBLEM: ['o', 'h', 'z', 'n', 'e', 'y', 't', '4371', 'm', '1059', '4853', '8529', 'l']

SOLUTION: e, h, l, m, n, o, t, y, z

PROBLEM: ['i', '3501', 'b', 'v', '7951', 'u', 'y', 'c', '2547', '2815', 'c', 'a', '7725', 'y', '4621', '5685']

SOLUTION:
a, b, c, i, u, v, y