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: ['o', '5503', '5837', '4539', '7631', 'm', '2641', 'p', '7901', '8117', 'z', '3373', '3215', 'v', 'a', '5949', 'w', '9049', 'd', 'a', 'l', 'v', 'l', 'n', 'w', 'r', 'j', '9031', '9609', '4209', 'c', '7453', '5855', '2883', '5941', 't', '4283', 'x', 'x', 'n', 'c']

SOLUTION: a, c, d, j, l, m, n, o, p, r, t, v, w, x, z

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: ['7369', '6577', 'f', '441', '4147', '3843', '7963', '6879', 'e', 'f', 'f', 'q', '4247', '2857', '319', 'e', '7535', 'l', 'f', '6879', '8485', '9369', '2633', '8519', '7279', 'a', 'q', '249', 'x', '6451', '1761', '1597', 'w', 'n', 'l']

SOLUTION:
a, e, f, l, n, q, w, x