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:
['7561', 'r', '3419', 'k', 's', '5997', 'u', '6635', '7003', '8491', 'i', '9835', 'c', '8827', 'h', 'a', 'j', '7675', '1995', '1223']
answer:
a, c, h, i, j, k, r, s, u


question:
['491', '229', 'g', '6677', '4793', 'h', 'x', 'a', '2333', 'u', 'l', '785', 'p', '7331', '653', '5193', '5415', '8417', 'v']
answer:
a, g, h, l, p, u, v, x


question:
['p', '2635', 'k', 'y', 'i', 'm', '1079', 'f', 'q', 'h', 'x', 'z', 'n', 'q', '1615', '3179', 'n', '9583', '521', '6557', '4505']
answer:

f, h, i, k, m, n, p, q, x, y, z