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: ['7561', 'r', '3419', 'k', 's', '5997', 'u', '6635', '7003', '8491', 'i', '9835', 'c', '8827', 'h', 'a', 'j', '7675', '1995', '1223']

SOLUTION: a, c, h, i, j, k, r, s, u

PROBLEM: ['f', 'a', 'i', 'y', 'j', 'b', '1001', '6795', 'e', '9265', '4587', '4249', 'o', 'h', '2711', '1377', '1899', '2147']

SOLUTION:
a, b, e, f, h, i, j, o, y