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: ['9627', '9879', '5421', '4755', '1533', '6727', 't', '7641', 'd', '3929', 'h', '3989', '8441', 'k', 'p', '2653', 'm', 'b', 'i', '3431', '4907', '5687', 'g', 'h', '9185', '5051', 'k', '7135', '709']

SOLUTION: b, d, g, h, i, k, m, p, t

PROBLEM: ['2349', 'p', 'a', '435', 'y', 'h', '3249', 'o']

SOLUTION: a, h, o, p, y

PROBLEM: ['o', '1823', '2759', '8145', '3867', '4407', 'z', '1621', 'e', '6393', 'q', 'f', '5509', '2949', 'a', 'e', 'q', '3945', 'h', '667', 'p', 'l', 'l', 'p', 'b', 'j', '2605', '3839', 'y', '1747', 'p', 'y', '9853', 'a', '8871', 'v', 'k', 'd', '6223', '531', 'r']

SOLUTION:
a, b, d, e, f, h, j, k, l, o, p, q, r, v, y, z