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: ['4925', 'i', 'q', 'k', '7615', 'r', '7217', 'o', '8097', '9151']

SOLUTION: i, k, o, q, r

PROBLEM: ['o', 'm', '8015', '787', '4787', '1727', 'f', 'e', 'c']

SOLUTION: c, e, f, m, o

PROBLEM: ['4743', '3547', '1547', '365', 'k', '3177', '6221', '8695', 'g', 'r', 'j', '5873', 'c', '1921', 'v', 'w', 'd', '2861', 'a', 't', 'r', 'u', 'a', 'c', '8315', '9439', '2083', 't', 'i', '5477', 'h', 'k', '2565', '1639', 't', '7841', 'b', '5623', 'e', 's']

SOLUTION:
a, b, c, d, e, g, h, i, j, k, r, s, t, u, v, w

