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.
--------
Question: ['l', '6313', '3199', 'w', '249', '8747', '7391', '3871', '173', 'x', 'o', '8647', '4413', '3645', '6123', '701', 'q', '2147', '4289', '7333', '533']

Answer: l, o, q, w, x


Question: ['l', 'u', '3901', '341', '5801']

Answer: l, u


Question: ['r', '3851', 'f', '973', 'g', 'q', 'n', 't', 'k', 'b', 'b', '5121', '2481', '7843', '463', '4577', 't', 'a', '4175', '6325', 'r', 'k', 'y', '5901', 'q', '1741', '887', '6821']

Answer:
a, b, f, g, k, n, q, r, t, y