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: ['w', '743', '5757', '8731', 'k', 'p', '317', 'n', 'x', '5649', 'l', 'm', 'c', '2499', 'l']

SOLUTION: c, k, l, m, n, p, w, x

PROBLEM: ['p', '5229', '7521', 'y', 'n', 'u', 'c', '4047', '781', 'a', '4707', '7149', 'j', 'm', 't', '515', '7691', 'h', '4879', 'j', '6593', 'n', 'p', '2949', '1343', 'y', '2629', 'p', 'b', 'b', '2861', 'a']

SOLUTION: a, b, c, h, j, m, n, p, t, u, y

PROBLEM: ['219', '2065', '4045', 'k', 'n', 's', 'z', '7239', '1043', 'r', '2333', 'q', 'k', 'b', '2013', 'g', '6925', '9835', 'a', '5377', 'k', '8005', 'p', '9753', 'm', '201', '2353', 'f', 'n', '89', 'q', 'p', '7847', 's', 'l', '3359', '2269', 'v', 'm', '8247', '9665', 'u', 'w']

SOLUTION:
a, b, f, g, k, l, m, n, p, q, r, s, u, v, w, z