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: ['5859', 'x', 'z', 'v', 'l', 'z', 'g', 't', 'x', '341', '7023', '4937', 'b', 'n', 'y', 't', 's', '1369', '4461', 'f', '1315', 'l', '5221', '6583', 'h', 'j', 't']

SOLUTION: b, f, g, h, j, l, n, s, t, v, x, y, z

PROBLEM: ['a', '7599', 'i', '9455', '3955', '2015', 'j', '7345', 'x', 't', 'c', '1317', '9155', '6383', '7793', 'n', '5581', 'v', '3485', 'n', 'r']

SOLUTION:
a, c, i, j, n, r, t, v, x