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:
['w', '1367', '5389', '9515']
answer:
w


question:
['1197', '305', 's', '1113', 'n', '2207', 'e', '227', '2833', '607', '3049', 'v', '4615', 'a', 'k', 'r', 's', '3571', 'f', '4215', 'f', '8985', '5559', '4111', 'u', '1433', '1943', '8831', 'w', 'x', 'o', '9023', 'u', 'y', 'p', 's', 'h', '8877', 'p', 'n', '8903', '5811']
answer:
a, e, f, h, k, n, o, p, r, s, u, v, w, x, y


question:
['3505', '3877', '9161', 'j', '7219', 'x', 'p', 'g', 'l', '9843', '6269', '9215', '3423', 'b', '7543', '2211', '6869', 'w', 'r', '3129', 'h', '2869', 'd', 'e', '4147', 'r', 'y', 't', '7763', 'm', '7675', '1607', 'i', 'n', 'e']
answer:

b, d, e, g, h, i, j, l, m, n, p, r, t, w, x, y