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: ['7123', 'm', 'h', '4065', 'c', 'n', '187', '3899', 'r', 'k', '2071', '9481', '6277']

SOLUTION: c, h, k, m, n, r

PROBLEM: ['5957', 'd', 'i', 'b', 'e', '5565', 'c', 'i', '2919']

SOLUTION: b, c, d, e, i

PROBLEM: ['8733', 'j', 'q', 'b', 'e', 'n', '1947', 'f', 'v', '4045', '5569', 'p', '5011', '3245', '2809', '5549', 'z', 'w', 'n', 'u', '9579', '4213', '1863', 'b', '1317']

SOLUTION:
b, e, f, j, n, p, q, u, v, w, z