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.

['7997', 'm']
m

['k', 'c', 'i']
c, i, k

['z', '5121', 'c', '965', '5043', 'o', 'b', '2307', 'w', '2143', 'u', 't', 'e', '1691', 'g', '9447', '6335', 'u', '9035', '5393', '3581', 'n', '9843', 'h', 'l', 't']

b, c, e, g, h, l, n, o, t, u, w, z