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: ['9467', 'o', '8347', '7125', '7999', '1737', 'h', '7043', '8617', '2033', '9959', '2349', 'p', '9389', '5525', 'w', 'u', 'p', '4703', '9807', 's', 'f', '2359', '7357', '2471', '5447', 'f', 'w', '2865', '6627', '3211', 'y', '23', 'z', 's', '1517', '3553', 'r', '2251']

SOLUTION: f, h, o, p, r, s, u, w, y, z

PROBLEM: ['8821', '9833', 'l']

SOLUTION: l

PROBLEM: ['w', '9663', 's', 'p', 'c', '2957', 'u', '7015', '7785', 'm']

SOLUTION:
c, m, p, s, u, w