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.

['y', 'g', '107', '4899', '6357', '9777', 'k', '1865', '7029', 'q', 'x', '7051', 's', '6125', '4285', '2731', 'z', 'a', '737', '6137']
a, g, k, q, s, x, y, z

['5345', 'f', '6605', 's', 'q', 'w', 'p', 'o', 's', 'u', 'i', '7339', '8379', 'h', '9547', 'b']
b, f, h, i, o, p, q, s, u, w

['9409', '8861', '5517', 'e', 'l', '3159', 'c', 'd', 'i', '7009', 'y', '5129', '635', 'b', '7481', 'e', 'x', '8417', 'p', 'e', '5475', 'l', '8869', '9519', '3285', '2827', 'z', '6125', 'j', 'i', 'x', 'u', 'u']

b, c, d, e, i, j, l, p, u, x, y, z