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: ['9579', 'm', 'v', 'r']

SOLUTION: m, r, v

PROBLEM: ['g', 'p', '2925', 'n', 'o', 'y', '6381', 'l', '4963', 'g', 'm', 'u', 't', '9389', '3787', '7713', '1251', '779', 'i', 'w', '9869', 'y', 'y', '3881', 'k', 't']

SOLUTION: g, i, k, l, m, n, o, p, t, u, w, y

PROBLEM: ['2553', 'c', '3401', 'r', 'e', '5561', '8589', 'c', '89', '2399', '4861', 'h', '9461', '3347', 'f', 'b', '897', '8133', 'a', '7369', '6977', '73', '4995', 'k', '1733']

SOLUTION:
a, b, c, e, f, h, k, r