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: ['p', '2923', 'e', 'k', '5433', '605', '5079', 'k', 'p', 'x', '4845', '4099', '6795']

SOLUTION: e, k, p, x

PROBLEM: ['6597', '7889', 'x', 'v', 'm', 'j', 'j', 'w', 'v', '177', 'x', '8353', '5897']

SOLUTION: j, m, v, w, x

PROBLEM: ['m', 'u', 'w', 'u', '3293', 'r', '7905', '7933', '2661', 'o', 'a', '7123', 'n', 'x', 'n', 'e', 'b', 'c', 'b', '9141', '4945', '7559']

SOLUTION:
a, b, c, e, m, n, o, r, u, w, x