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: ['9555', '5983', '1853', 'c', 'z', 't', 'p', '9041', 'd', '5919', '1621', '345', 's', '2647', '4261', '8611', 'w', 'x', 'p', '9103', '2599', '5101', '9261', 'k', '7437']

SOLUTION: c, d, k, p, s, t, w, x, z

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

SOLUTION: j, m, v, w, x

PROBLEM: ['989', '7951', 'b', 'p', '9137', 'b', 'f', 'g', '3645', 'c', 'b', '8459', 'n', '2247', 'a', '7739', 'h', '6539', 'f', 'a', 'i', 'u', '9669', '2293', '8115', '2219', 'w', 'p', '5935', '2547', '8033', '4135', '5555', 'o', 'c', 'o', '7531', '5335', 'y', 'k', '341', '9475']

SOLUTION:
a, b, c, f, g, h, i, k, n, o, p, u, w, y