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

Answer: a, g, k, q, s, x, y, z


Question: ['9467', 'o', '8347', '7125', '7999', '1737', 'h', '7043', '8617', '2033', '9959', '2349', 'p', '9389', '5525', 'w', 'u', 'p', '4703', '9807', 's', 'f', '2359', '7357', '2471', '5447', 'f', 'w', '2865', '6627', '3211', 'y', '23', 'z', 's', '1517', '3553', 'r', '2251']

Answer: f, h, o, p, r, s, u, w, y, z


Question: ['g', '4651', '4461', '3479', '7497', '9355', '5229', 'w', '1045', 'y', 'g', 'e', '8823', 'h', '1173', '5371', '8253', '9607', 'a']

Answer:
a, e, g, h, w, y