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: ['3797', '6117', 'x']

SOLUTION: x

PROBLEM: ['a', 'y', '7401', 'e', 'l', '4351', 'p', '5673', 'k', '333', 'o', 'd', 'e', 'j', 'e', '9569', '1795', 'r', 'z', '6059', '4399', '2927', 'n', '9387', '9317', 'b', 'c', 'e']

SOLUTION: a, b, c, d, e, j, k, l, n, o, p, r, y, z

PROBLEM: ['f', 'n', 's', '6871', 'o', '6457', 'p', '9187', 'r', '4565', '6715', 'u', 'j', 'q', '8897', '3785', '9503', 'r', 'g', 'p', 'f', '5185', '4751', 'z', 'e', 'v', '7275', '9329', 'k', 'm', 'o', '6105', 'd', 'y', 'p', '6799', 'a', 'r']

SOLUTION:
a, d, e, f, g, j, k, m, n, o, p, q, r, s, u, v, y, z