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:
['9385', '4021', 'y', '9629', 'u', '7623', 'd', '5155', 'x', '2605', '8893', 'l', 'p', 'a', 'm', '6699', 'i', '4503', '6623', 'm', 'l', '6115', 'p', 'w', '9691', '811', '4769', '2659', 'x', 'c', '6513', '5499', 's', 'q', 'f', 'v', 'z', 'w', 'z', '1361']
answer:
a, c, d, f, i, l, m, p, q, s, u, v, w, x, y, z


question:
['3797', '6117', 'x']
answer:
x


question:
['x', '7055', 'r', 'l', 'q', '3255', '9125', 'b', 'c', '3561', '6671', 'u', 'f', 'h', 'p', 'u', '4307']
answer:

b, c, f, h, l, p, q, r, u, x