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: ['6175', '9441', '7127', '5979', 's', '1367', 'e', 'm', '7083', '1787', '8375', '2851', '3475', 'r', '697', 'g', 'z', 'm', '4207', 'c', '7971', 'z', '9339', 'd', 's', '3507', '9003', 'i', 'y', 'w', 'j', 'i']

SOLUTION: c, d, e, g, i, j, m, r, s, w, y, z

PROBLEM: ['e', '1251', 'y', '6689', '6389', 'h', 't', '503', '5093', 'e', '923', '7051', 'm', 'u', '4501', '3289', '6887', '8341', 'o', '3671', 'n', 'w', '7749', 's', 'j', 'o', '8429', 'q', 'v', 'p', 'd', 'g', 'i', 'f']

SOLUTION: d, e, f, g, h, i, j, m, n, o, p, q, s, t, u, v, w, y

PROBLEM: ['5533', 'g', 'a', 'g', '8027', '6661', 'd', '7957', '5491', '509', 'g', 'w', 'l', '7573', 'u', 'o', '5119', 'h', 'v', '2543', 'e', 'm']

SOLUTION:
a, d, e, g, h, l, m, o, u, v, w