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: ['k', '8917', '3773', '6723', 'r', 'z', '3265', 'o', 'f', 'q', '9343', 'f', '1925', 'u', 'b', 'o', '5275', 'b', 'n', 'd', 'j', '4825']

SOLUTION: b, d, f, j, k, n, o, q, r, u, z

PROBLEM: ['2925', 'i', 'x', 's', 'j', '2007', '7413', '5723', '9285', 'w', '3663', 'l', '2399', 'd', '8399', '391', '6621', 'i', 'u', 'f', '9969', '3141']

SOLUTION:
d, f, i, j, l, s, u, w, x