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: ['m', '7517', '9361', '9567', '8785', 'k', '5699', '3585', 'v', '1913', '1651', 'g', 'p', '2731', 'q', 'h', '467', 'r', '1091', '9801', 'a', '6645']

SOLUTION: a, g, h, k, m, p, q, r, v

PROBLEM: ['5011', 'l', '925', 'e', 'b', '3077', 'm', '4541', '781']

SOLUTION: b, e, l, m

PROBLEM: ['8355', 'k', 'd', '4729', '6905', '6297', '7599', 't', '289', 'o', 'o', 'n', '8401', '8365', '9613', '8813', 'i', 't', '7277', 'v', 'k', 'u', '4735', 'u', '903', 'r', 'x', '4027', 'r', 'v', 'b', '9811', '6841', 'i', '9589', 'h', 'o', '5981', '8463', '5019', '6793', '4201', '1153']

SOLUTION:
b, d, h, i, k, n, o, r, t, u, v, x