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: ['a', 'a', 'b']

SOLUTION: a, b

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: ['v', 'n', 'e', 'c', '605', 'b', 'q', '1825', 'v', 'o', 'f', 'g', 'u', '8139', '4541']

SOLUTION:
b, c, e, f, g, n, o, q, u, v