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: ['8527', 'p', '4697', '8415', 'v', 'l', '2669', '2649', '4349', '4201', 'r', '7573', '2041', 'f', '8047', 'u', 'm', 'm', 'j', '5695']

SOLUTION: f, j, l, m, p, r, u, v

PROBLEM: ['u', '4731', 'l', 'p', '1997', '601', 'n', 'l', 'p', '211', '7355', '6537', 'w', 'x', '1741', '8145', '3689', 'm', 'y', '6945']

SOLUTION: l, m, n, p, u, w, x, y

PROBLEM: ['i', '8989', '8995', '347', '2793', 'm', 'a', 'd', 'g', '2599', '1581', '6791', '2741', 'g', 'z', 'b', '2951', '2955', 'v', 'l', 'd', 'd', 'f', 'c', '6937']

SOLUTION:
a, b, c, d, f, g, i, l, m, v, z