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: ['5159', '6407', '4021', '6655', 'c', 'k', 'w', '7191', 'l', '4321', '1609', 'm', '1991', '9261', '511', 'p', '7495', 'b', 'e', '4647', '2711', 'd', 'y', '3835', '5037', '3613', '2695', '3367', 'm', 'j', 'y', '9561', '4889', 'a', 'z', '2253', 'p', 't', 's', '8371', '2859', 's']

SOLUTION: a, b, c, d, e, j, k, l, m, p, s, t, w, y, z

PROBLEM: ['y', 'i', '257', '3695', 's', '6717', '4817', '4117']

SOLUTION: i, s, y

PROBLEM: ['6823', 's', '1047', '8765', 'd', 'o', '9007', '3401', 'e', 'm', 'o', '4593', 'p']

SOLUTION:
d, e, m, o, p, s