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: ['a', 'i', '7725', '2483', 'e', 'j', '5337', 'b', '6835', '8231', 'm', 'v', 'a', '1475', 'n', '5823', 's', 'm', '7313', '2841', '2585', '4673', 'u', '2083', 'z', 'd', 'p', '2117', 'i', '587', 'i', 'a', '2527', '7967', '6567', 'n', '6145', 'r', 'f']

SOLUTION: a, b, d, e, f, i, j, m, n, p, r, s, u, v, z

PROBLEM: ['w', 'n', '729', '2491', 'n', 'x', '915', '1869', 'z', '8491', '9947', '561', '829', 'n', 't', 'i']

SOLUTION: i, n, t, w, x, z

PROBLEM: ['2253', 'q', 'q', 's', 'w', '9969', 'z', '9755', 'r', 'b', 'l', 'o', '6815', 't', '7009', 'a', 'n', 'm', '747', '7861', 'j', 'r', '6179', '9547']

SOLUTION:
a, b, j, l, m, n, o, q, r, s, t, w, z