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.

['9923', 'x', '1901', 'v', '1459', '7503', '3829', '4929', 'k', 'c', '3329', '8793', 'n', 'a', '7249', 'b', 'l', 'l', 'm', 'p', 'b', 'a']
a, b, c, k, l, m, n, p, v, x

['o', 'h', 'z', 'n', 'e', 'y', 't', '4371', 'm', '1059', '4853', '8529', 'l']
e, h, l, m, n, o, t, y, z

['7921', '4657', '159', '221', '1777', 'm', '6757', 'x', '8747', '2517', 'n', 'x', 'n', 'q', '49', '9969', '8347', 'c', '3725', '9347', 'g', 'f', '1827', '3015']
c, f, g, m, n, q, x