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: ['o', 'l', 'm', 't', '4487', '1019', '9903', 'c']

SOLUTION: c, l, m, o, t

PROBLEM: ['x', '4283', 'n', 'b', 'g', 'p', '8305', '7781', '5907', 's', '1305', 'w', '8623', 'o', 'c', 'u', '1839', '2869', '7537', 'y', '2395', '5309', 'e', '4059', 'l', '6647', 'p', '9717', 'y', 'y', '3769', '2527', '2981', '5255', '4063', 'j', '4843', 'j', '9355', 'z']

SOLUTION: b, c, e, g, j, l, n, o, p, s, u, w, x, y, z

PROBLEM: ['c', 'v', 'z', 's', '319', 'c', '6373', '2797', '6371', 'i', 'a', 'w', 'v', 'z', 'b', 'c', 'd', 'h', '7523', '9407', 'b', '6347', '2827', '8843', '5729', 's', 'x', 'w', '639', 'k', 'e', '8991', 'k', '8951', '1087', '7889', '9685', 'g', 'a', '1325', 's', 'p', '6983', 'f', 's']

SOLUTION:
a, b, c, d, e, f, g, h, i, k, p, s, v, w, x, z