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: ['2181', '7019', 'l', 'z', 'z', 'y', '1245', '4179', '6951', '7249', '2723']

SOLUTION: l, y, z

PROBLEM: ['k', '8917', '3773', '6723', 'r', 'z', '3265', 'o', 'f', 'q', '9343', 'f', '1925', 'u', 'b', 'o', '5275', 'b', 'n', 'd', 'j', '4825']

SOLUTION: b, d, f, j, k, n, o, q, r, u, z

PROBLEM: ['7301', '7999', 'x', 'r', '6881', 'e', '609', 's', '7495', 'a', 's', '1961', 'q', 'x', '373', '6289', '4847', '5969', 't', '5487', '7639', '9039', '2395', 'b', 'd', '1447', 's', '8137', 's', '443', 'f', 'z', '4823', 'k', 'i', 'o', '4739', 'w', 'f', '8853', 'a']

SOLUTION:
a, b, d, e, f, i, k, o, q, r, s, t, w, x, z