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.

['w', 'n', '729', '2491', 'n', 'x', '915', '1869', 'z', '8491', '9947', '561', '829', 'n', 't', 'i']
i, n, t, w, x, z

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

['5893', 'm', 'm', 'e', '9549', '6881', 'x', '5635', 'd', '1341', 'l', 'i', 'n', 'z', 't', '6485', 'y', '2619']

d, e, i, l, m, n, t, x, y, z