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:
['b', 'd', '8153', 'u', '3695', '5317']
answer:
b, d, u


question:
['163', 'x', 'g', '5997', 'm', 'l', '7225', '7907', '375', 'y', 'a', 'j', 'c', 'j', '7755', '147', 'h', '3845', 'y', 's', 'h', 'u', '8737', '6091', 'j', 'f', 'c', '7395', '881', '1771', 'y', '3691', 'h']
answer:
a, c, f, g, h, j, l, m, s, u, x, y


question:
['1389', 'f', 'y', 'f', '5635', '8299', 's', 'r', '3801', '5493', '315', 's', 's', '5651', 'k', '6313', '4729', 'u', '877', '8887', 'j', 's', 'i', '4019', 'b', '1715', 'h', 'w', 'o', '2947', '6789', '4133', 'm', 't', '9667', 'r', '5273', '2093', 'n', 'z', 'p', '3475', 'o', '3861']
answer:

b, f, h, i, j, k, m, n, o, p, r, s, t, u, w, y, z