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', '6291', '3939', '9569', 'u', '1635', '3359', '8335', 'n', '2799', '7359', 'k', 'm', '2817']

SOLUTION: k, m, n, u, w

PROBLEM: ['3147', '9807', '5313', '6311', '737', '1555', '5803', '3437', '5665', '3973', 'o', 'f', '7871', '1721', '7833', '2933', 'b', 'b', 'n', 'm', 'k']

SOLUTION: b, f, k, m, n, o

PROBLEM: ['m', '9149', '6801', 'p', 'q', 't', 'z', '3053', '8645', 'g', '6677', 'v', 'o', '2193', '8083', 'u', 'o', '9179', '17', '1861', 'c', 'x', 'e', 'w', '7047', '6873', '771', '1551', 'r', 'j', '9491', '2131', 'u']

SOLUTION:
c, e, g, j, m, o, p, q, r, t, u, v, w, x, z