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: ['r', 'n', '7583', '8697', '7927', 'l', '5003', '1363', 'p', 'e', 'q', '6227', '6915', '8619', '9011', 'n', '3063', '3799']

SOLUTION: e, l, n, p, q, r

PROBLEM: ['4927', 'h', 'x', '4719', 'j', 'f', '7797', 'l', 'i', 'q', 'x', 'i', 'k', '3215', 'k', '1625', 'g', 't', 'i', 'w', 'n', '6659', '8355', '831', 'h', '9723']

SOLUTION: f, g, h, i, j, k, l, n, q, t, w, x

PROBLEM: ['w', 'k', '3231', '3553', 'z', 'o', 'r', 'k', '5017', '3905', '6863', 'i', 'l', 'p', '3773']

SOLUTION:
i, k, l, o, p, r, w, z