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: ['9923', 'x', '1901', 'v', '1459', '7503', '3829', '4929', 'k', 'c', '3329', '8793', 'n', 'a', '7249', 'b', 'l', 'l', 'm', 'p', 'b', 'a']

SOLUTION: a, b, c, k, l, m, n, p, v, x

PROBLEM: ['t', 'h', '6141', 'g', 'f', 'z', 'n', 'b', 'k', '9059', 'y', 'p', '4289', '2683', 'a', '3267', 'w', 'p', 't', '3623', '7759', 'a', 'o', 'm', '9815', 'q', 'u', '8051', '6871']

SOLUTION: a, b, f, g, h, k, m, n, o, p, q, t, u, w, y, z

PROBLEM: ['c', 's', '4487', '1453', '203', 'r', 'r', 's', 'q', 'u', '2421', '7955', '7399', 'n', 'm', '2945']

SOLUTION:
c, m, n, q, r, s, u

