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: ['r', 'q', '3649', 't', '3941', 'z', '3729', 's', 'g', '6905', 'h', 'v', '1085', '6353', 'a', '9395', '5433', 'a', '2565', 'p', 'a', 'h', '1491', 'j', 'b', 'v', 'e']

SOLUTION: a, b, e, g, h, j, p, q, r, s, t, v, z

PROBLEM: ['y', 'g', '107', '4899', '6357', '9777', 'k', '1865', '7029', 'q', 'x', '7051', 's', '6125', '4285', '2731', 'z', 'a', '737', '6137']

SOLUTION: a, g, k, q, s, x, y, z

PROBLEM: ['697', '783', 'w', '9775', '5939', '3239', 'l']

SOLUTION:
l, w