instruction:
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:
['n', '9571', '2983', '7597', 'v', 'y', '1993', '1403', '8309', '7043', 'c', '7329', 'p', '4479', 'p']
answer:
c, n, p, v, y


question:
['7653', 'n', '697', '4565', 't', '7275', '2429', '1365', '7059', 'o', '8053', 'j', '2837', '957', '851', 'z', 'd', 'd', 'y', 'c', '7467', 'o', 'i', '9519', 'q', 'g', '7911', 't', 'g', '3439', '5821', '8433', 'k', 'z', 's', 'g', '685', 'i', 't', 'r', '6881']
answer:
c, d, g, i, j, k, n, o, q, r, s, t, y, z


question:
['4811', '4281', 'b', '2069', 'p', 'b', 'u', 'x', '5907', 'w', '3991', '595', 'i', 'q', '3847', 'f', '267', 'n', 'o', '8665', 'z']
answer:

b, f, i, n, o, p, q, u, w, x, z