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:
['o', 'l', 'm', 't', '4487', '1019', '9903', 'c']
answer:
c, l, m, o, t


question:
['m', '6537', '4063', '6413', 'k', 'd', '2479', 'p', '2251', 'q', '7079', 'r', 'd', 'p', '3347', '1391', '9847', '4487', 'u', '6951', '5285', '5837', '6747', 'r', 's', 'c', 'x', 'b', 'q', 'y', 'd', '331', '679', 'v', '1919', 'f', 'p', '1267', '3151']
answer:
b, c, d, f, k, m, p, q, r, s, u, v, x, y


question:
['1865', 'n', '25', 's', '7401', '719', '73', 'g', '1611', 'w', 's', 'v', '6095', 'o', 'd', 'v', 'i', 'q', '4261', 'z', 'm', '3899', 'p', '4035', 'o', 'b', '7065', '5545', '8875', 'u', 'h', 'p', '687', '8691', '8987', 'q', '3483', '2849', '4233', '2939', 'w', 'b', 't']
answer:

b, d, g, h, i, m, n, o, p, q, s, t, u, v, w, z