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: ['6249', '1235']

SOLUTION: -1

PROBLEM: ['2313', '2073', 'd', 'e', 'o', '793', '4999', 'f', 'c', '4473', '4519', 'u', 'n', 'k', '69', '475', 'a', 'j', 'q', 'x', '5869', '9523', 'z', 'v', '9265', '5989', 'p', 'm', 'g', 'y', 'b']

SOLUTION: a, b, c, d, e, f, g, j, k, m, n, o, p, q, u, v, x, y, z

PROBLEM: ['4509', 't', 'b', '4447', '9483', '8643', '4353', 't', 'x', 'i', '9399', '6495', 'p']

SOLUTION:
b, i, p, t, x