TASK DEFINITION: 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.
PROBLEM: ['8319', 'f', 'w', 'w', 'v', '6521', '4503', 'b', 's', 'b', '9651', 'k', '4635', '2195', '7537', '6839', 'i', 'd', 'b', '205', 'q', '7333', 'q', '5129', '4921', 's']

SOLUTION: b, d, f, i, k, q, s, v, w

PROBLEM: ['6143', 'y', '5505', '9813', 'r', 'v', 'u', '8681', '2387', 'u', 'o', 'm', '9793', 'm']

SOLUTION: m, o, r, u, v, y

PROBLEM: ['463', 'x', 'z', 'y', 'n', 'g', '5973', '2771', '773', 'e', '7507', 'z', '9493', 'q', 'v', 'g', 'r', '7615', '9497', 't', 'l', '5379', 's', '4431', 'b', '8259', '2269', 'f', 't', '1957', '5521', 'c', 'f', 'd', '4807', '4525', 'n', 'y', 'u', '5515', '8129']

SOLUTION:
b, c, d, e, f, g, l, n, q, r, s, t, u, v, x, y, z