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: ['1985', '729', '169', '1299', 'l', 'z', '6809', '3083', 'w', 'f', '1989', 'z', '889', 'x', 'r', '1601']

SOLUTION: f, l, r, w, x, z

PROBLEM: ['9013', 'e', 'm', 'p', 'k', '161', 'k']

SOLUTION: e, k, m, p

PROBLEM: ['729', '3837', '997', 'f', 't', 'z', '7459']

SOLUTION:
f, t, z

