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: ['1985', '729', '169', '1299', 'l', 'z', '6809', '3083', 'w', 'f', '1989', 'z', '889', 'x', 'r', '1601']

SOLUTION: f, l, r, w, x, z

PROBLEM: ['7911', '7175', 'y', '9173', 'y', '2529', '831', 'k', '7197', 'j', '2343', 'i', 'b', '6799', '5987', '7277', 'n', 'x', 'h', '7209', 'l', 'd', 'm', 'e', '2277', '8909', 'x', '5361']

SOLUTION: b, d, e, h, i, j, k, l, m, n, x, y

PROBLEM: ['2117', '2707', 'a', 'b', '8981', '6943', '901', '8521', '6953', '4843', '9555', 'q', 'd', 'm']

SOLUTION:
a, b, d, m, q