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: ['c', '7039', 'g', '1899', 'r', '507', 'c', '2587', '3865', '1729', '3927', 'r', '3535', '2791', 'm', 'l', 'r']

SOLUTION: c, g, l, m, r

PROBLEM: ['m', 'b', 'd', 'l', '3303', '523', 'v', 'o', 'u', 'm', 'g', '8193', 'i', '7361', '3219', 'u', '4661', 'c', 'e', 's', '8279', '4875', '4465', 'w', 'l', '8009']

SOLUTION:
b, c, d, e, g, i, l, m, o, s, u, v, w