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: ['4041', 'l', 'g', '9571', '9295', '1395', 'l', 'p', 'f', 'w', 'g', '1721', '2421', 'w', 'z', '2235', 'p', '7851']

SOLUTION: f, g, l, p, w, z

PROBLEM: ['f', 'a', 'r', '4009', 'k', 'a', 'g', '7725', 'v', 'b', '6705', 'a', '6583', '3159', 'c', 'w', 'x', 'h', '7625', 'p', 'y', '5645', 'k', 'r', 'j', '4175', 'r', '3103', '8631', '5999', 'p', 'g', 'h']

SOLUTION: a, b, c, f, g, h, j, k, p, r, v, w, x, y

PROBLEM: ['f', '8577', '9251', 'a', '6803', '8637', 's', 'q', 's', 'x', 'k', 'm', '6413', 'o', '1293', '7663', '665', '8617', '8349', 'h', '2253', 'c', 'x', 'g', '1185', 'm', 'l']

SOLUTION:
a, c, f, g, h, k, l, m, o, q, s, x