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: ['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: ['895', '2049', '8839', '1773', 'v', '467']

SOLUTION: v

PROBLEM: ['w', 'q']

SOLUTION:
q, w