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: ['j', 'y', '9907', 'a', '5715', 'l', '9817', '1949', '2697', '2255', '9571', '8957', '9329', '6055', 'z', 'q', '1185', '4593']

SOLUTION: a, j, l, q, y, z

PROBLEM: ['k', 'v', 'e', '6377', 'y', '3585', '4535', 'f', 'g', 'm', 'f', '8369', 'v', '7445', '4527', '9383', 'n']

SOLUTION: e, f, g, k, m, n, v, y

PROBLEM: ['6233', 'f', 'x', 'c', 'f', 'h', 'z', '2453', 'u', 'w', '5399', 'c', 'a', 's', '3481', '2669', '1509', '8277', 'y', 'p', '2325', '4057', '2273', '797', '9243', '4281', '7173', '8029', '7453', '5675', '8139', '9811', 'l', 'x', 't', 's', 'd', 'a', '7959', '1247', 's', '9405']

SOLUTION:
a, c, d, f, h, l, p, s, t, u, w, x, y, z