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: ['5337', '4877', '9443', '3445', 'u', '2571', 't', 'n', 'x', '1985', '5145', '3397', 'p', '9259', 's', 'x', 'u', 'c', 'g', 't', 'j', '829', '8273', 'e', 'j', 'r', 'x', '865', '4773', 'h', '4407', '8591']

SOLUTION: c, e, g, h, j, n, p, r, s, t, u, x

PROBLEM: ['5761', '2289', '577', 't', '125', 'i', 'g', '9693', '747', 'd', '4829', '9587', 'f', 'k', 'w', 'v', '8607']

SOLUTION: d, f, g, i, k, t, v, w

PROBLEM: ['k', 'f', 'j', 'b', '7819', 'x', '5485', 'y', '191', '9365', 'y', '6391', 'h', 'l', 'x', '3265', '3417', '6355', 'u', '5427', '7053', 'h', 'z', 'c', '4641', 'a', '1505', 'f', 'a', '7893', 'v', '7899', '7055', '5565', 'd', 'i', '9695', '9951', 'e']

SOLUTION:
a, b, c, d, e, f, h, i, j, k, l, u, v, x, y, z