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: ['w', '9437', 's', '9819', 'q', 'q', '4443', 'p', '377', '6777', 's', 'x', 'a', 'o', '9205', '9289', '7103', 'k', 'l', '9453', '9043', 'k', 'r', 'g']

SOLUTION: a, g, k, l, o, p, q, r, s, w, x

PROBLEM: ['s', 'w', '8949', '4025']

SOLUTION: s, w

PROBLEM: ['8387', 'x', 'u', 'm']

SOLUTION:
m, u, x