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: ['1627', 'r', '2429', 'b', '4451', 's', 'k', 'm', '269', 'l', '709', 's', 'q', '985', 'x', 'j', 'k', 'k', '6603', 'v', '9497', '477', '5803', 'c', 't', 'f', '3189', '6419', '8561', '5709', 'u', 'z', '5717', '9711', 'w', 'y', 'm', 'v']

SOLUTION: b, c, f, j, k, l, m, q, r, s, t, u, v, w, x, y, z

PROBLEM: ['749', 'r', 'a', 's', 't', '5905', 'm', 'd', '8437', '4583']

SOLUTION: a, d, m, r, s, t

PROBLEM: ['1841', 'b', '291', 'y', 'a', '9167', 'q', 'z', '2627', 'z', '8065', 'n', '6535', 'z', 'v', '8597', 'l', 'l', 't', '1807', '4123', '2367', 'k', 'x', 'r']

SOLUTION:
a, b, k, l, n, q, r, t, v, x, y, z