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.

['4749', '4607', '625', '6907', 't', 'b', '8479', '6505', 'r']
b, r, t

['2453', 'r', 'd', '8499', 't', 's', 'h', 'a', 'm', '9271', 'g', '2599', '6209', 'o', 'i', '4069', 't', '6793', '7679', '6643', '7359', 'm', 'f', 'w', '775', '3347', '6161', '9745', 'i']
a, d, f, g, h, i, m, o, r, s, t, w

['7029', 'p', '8279', 't', '5331', '7387', '8127', '9577', 'v', 'n', 'k', 'w', 'f']

f, k, n, p, t, v, w