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', 'g', 'd', 'p', '8163', '6643', 'o', 'p', 'm']

Answer: d, g, l, m, o, p


Question: ['m', '7807', 'n', 'w', '5097', '1023', '2723', 'u', '3055', '7285', 'f', 'm', 'w', '5197', '9743', '7519', '4451', 'c', 't', '1939', '5847']

Answer: c, f, m, n, t, u, w


Question: ['7127', 'h', 'r', '3775', 'q', 'p', 's', 'j', 'r', '3791', 'v', '5421', 'v', '4727', '7729', 'e', 'h', 'b', '9733', 'l', '7939', '7889']

Answer:
b, e, h, j, l, p, q, r, s, v