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: ['7591', '7521', 'm', '1429', 'x']

SOLUTION: m, x

PROBLEM: ['m', '8127', '7519', '4543', '2809', '9855', 'n', '6241', 'w', 'w', 'q', 'w', 'p', '8599', '7819', '3817', 'm', 'q']

SOLUTION: m, n, p, q, w

PROBLEM: ['6465', '8157', '4629', 'n', '4201', 'p', 'y', '2597', '9047', '5261', '2751', 'u', 'n', '2095', 'u', '6005', 'g']

SOLUTION:
g, n, p, u, y