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: ['q', 'g', 's', 'g', 'z', '987', '777']

SOLUTION: g, q, s, z

PROBLEM: ['2453', 'r', 'd', '8499', 't', 's', 'h', 'a', 'm', '9271', 'g', '2599', '6209', 'o', 'i', '4069', 't', '6793', '7679', '6643', '7359', 'm', 'f', 'w', '775', '3347', '6161', '9745', 'i']

SOLUTION: a, d, f, g, h, i, m, o, r, s, t, w

PROBLEM: ['n', '4477', '7155', 'v', '1555', '9323', 'w', 'o', '6849', 'c', 'i', '9597', 's', 'h', '8433', '8929', '9737', 'e', 'o', '219', 'i', '8285', 'b', '1471', 'h', 'b', 'y', 'j', '5513', 'e', 'z', 'w', '9581', 'y', 'w', '621', 't', 'y', 'x', '4013', '7789', 'x']

SOLUTION:
b, c, e, h, i, j, n, o, s, t, v, w, x, y, z