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: ['t', 'r', '2959', '2517', 'a', '9959', '729', '511', 'y', 'r', '465', 'c', '687', 'm', 'b', 'm', '3449', '9713', 'g', '8275', '8823', 'a', 'z', 'w', '2185', '6283', '8457', '8137', '7163', '8329']

SOLUTION: a, b, c, g, m, r, t, w, y, z

PROBLEM: ['815', '6967', '6553', 'r', 'y', '3641', 'q', 'b', '6131', '4289', 'w', '6093', '6055', 'i', 'b', 'y', '5107', 'v', 'g', '9709', 'x', 'i']

SOLUTION: b, g, i, q, r, v, w, x, y

PROBLEM: ['s', '4955', 'c', 'q', '4323', '6765', 'q', 'v', 'j', '5427', '3333', 'b', 'm', '8497', '2873', 'w', '4547', 'g', 'a', '5465', 'z', 'k', 'i']

SOLUTION:
a, b, c, g, i, j, k, m, q, s, v, w, z