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: ['t', 'u', 'y', 'y', 'b', 'x', 'q', '3713', '2679']

SOLUTION: b, q, t, u, x, y

PROBLEM: ['491', '229', 'g', '6677', '4793', 'h', 'x', 'a', '2333', 'u', 'l', '785', 'p', '7331', '653', '5193', '5415', '8417', 'v']

SOLUTION: a, g, h, l, p, u, v, x

PROBLEM: ['o', 'l', '6613', 'o', 'h', '2279', 'j', '4841', 'b', '4057', 'o', '2251', 'c', 'r', '8337', 'k', 'i', '4155', '4009', '4757', '3153', '7251', '4927', '423', 'e']

SOLUTION:
b, c, e, h, i, j, k, l, o, r