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: ['k', 'z', '303', 'a', 'f', 'q', 'i', '1475', '3453', 'd', 'w', '4037', 'z', 'h', 'k', '3547', '1561']

SOLUTION: a, d, f, h, i, k, q, w, z

PROBLEM: ['9013', 'e', 'm', 'p', 'k', '161', 'k']

SOLUTION: e, k, m, p

PROBLEM: ['y', '743', 'o', 't', '4417', 'x', '4039', 'y']

SOLUTION:
o, t, x, y