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

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

PROBLEM: ['c', 'e', '6509', '1295', 'u', '5445', '1731', '3049']

SOLUTION: c, e, u

PROBLEM: ['j', 'h', 'o', '9949', '763', '1667', 'x', '2853', 'h', '8061', '5471', 'i', '2297', 'o', 't', '9041', 'j', '2379']

SOLUTION:
h, i, j, o, t, x