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: ['m', '7517', '9361', '9567', '8785', 'k', '5699', '3585', 'v', '1913', '1651', 'g', 'p', '2731', 'q', 'h', '467', 'r', '1091', '9801', 'a', '6645']

SOLUTION: a, g, h, k, m, p, q, r, v

PROBLEM: ['1189', '7143', '993', '1513', '6449', '9749', '5963', '8159', 't', '3543', 'j', 'i', '4227', '1463', '6431', '4987', 'y', 'q', 'f', '321', 'm', 'r']

SOLUTION: f, i, j, m, q, r, t, y

PROBLEM: ['s', '7263', 'm', '2797', 'y', '8691', 'p', '3361', '8589', 'i', '7535', 'j', '5203', 'y', '8929', '5369', '9235', '7067', 'a', 'o', 'i', 'j', '8163', 'r', 'i', 'a', '7715', '5001', '2471', 'k', 'w', 'j', 'c', 's', '5245', '9565', 'f']

SOLUTION:
a, c, f, i, j, k, m, o, p, r, s, w, y