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: ['p', '2923', 'e', 'k', '5433', '605', '5079', 'k', 'p', 'x', '4845', '4099', '6795']

SOLUTION: e, k, p, x

PROBLEM: ['d', 'm', 'k', '3513', '8241', '5541', 'm', 's', '1993', '6163', '2753', 'd', 'b', 'm', 'i', '7647', '8631', '9119', '2165', 'x', '3911', '2769', '1673', '7195', 't', 'w', '5555', 'o', '3265']

SOLUTION: b, d, i, k, m, o, s, t, w, x

PROBLEM: ['f', '1371', 'a', 'v', 'v', '8679', 'd', '1643', '9057', 'a']

SOLUTION:
a, d, f, v