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: ['3947', '4809', 'b', 'a', '4769', '4179', '535', '5965', 'f', 'j', '2265', 'w', '3103', 'u']

SOLUTION: a, b, f, j, u, w

PROBLEM: ['2633', 'd', 'r', '8083', 'f', 'd', '5121', '8651', 'o', 'b', '811', '7551', 'x', 'p', 'm', 'v', 'm', '7833', '1959', 'y', 'p', '779', '1889']

SOLUTION: b, d, f, m, o, p, r, v, x, y

PROBLEM: ['5499', 'p', 'q', '99', 'h', '9247', 'u', 'i', 'y', '8831', '769', 'w', 's', 'i', '2523', 't', 'b', '4609', 'f']

SOLUTION:
b, f, h, i, p, q, s, t, u, w, y