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: ['5011', 'l', '925', 'e', 'b', '3077', 'm', '4541', '781']

SOLUTION: b, e, l, m

PROBLEM: ['p', 'k', 'i', '753', 'u', 'm', '3817', '1597', 'l', 'm', 'a', 'i', 'b', 's', 'c', '2561', 'x', '5363', '1173', '8657', '2033', 'b', 'p', '3093', 'k', '6535', '307', '9925', 'b', 'q', 'q']

SOLUTION: a, b, c, i, k, l, m, p, q, s, u, x

PROBLEM: ['3769', '1519', '2695', 'b', '2767', 'v', 'i', 'k', '9651', 'z', '2583', 'b']

SOLUTION:
b, i, k, v, z