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: ['2697', 's', '8733', 'n', '5871', 'f']

SOLUTION: f, n, s

PROBLEM: ['x', 'j', '9747', 'i', '2015', '3505', 'q', 'n', 'h', '3011', 'u', '8043', 'j', 'f', 'd', 'a', 'p', '5817', 'l', 'q', '2275', 'n', '7085', '5373', 'l', 'g', 'b', '8043', '3085']

SOLUTION: a, b, d, f, g, h, i, j, l, n, p, q, u, x

PROBLEM: ['5549', '3267', 'h', 'n', '8359', 'c', '1601', '103', 'i', '1291', 'x', '847', 's', '3647', 's', 'y', '5019', 't', 'b', 'f', 'r', 'i', '7677', 'm', 'w']

SOLUTION:
b, c, f, h, i, m, n, r, s, t, w, x, y