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: ['c', 'a', 'p', 'p', '4203', '1587', '2953', '9809', '99', '5821', 't', 'i', '4213', '1809', 's', 'l', 'i', 'b', '9233', '3983', '7713', '1807', 'k', 'f', '7825', '5491', 'o', '1347', 'u', 'h', '3967', 'u', 'g', '6775', '1069', '9211', 'i', '3369', 'r']

SOLUTION: a, b, c, f, g, h, i, k, l, o, p, r, s, t, u

PROBLEM: ['1945', 't', '4477', '4439', '6569', '2021', 'y', 't', '2725', '8947', '6921', '1373', '8107', 'g', 'c', 'w', 'x', 'b', '9117', 'k', '6567', '5073', '2307', 'e', 'b', '7405', 'e', 'x', '1419', 'd', 'o', 'n', 'a', '2647', 'z', '1459', 'n', '6137', 'u', 'b', 'q', '4459']

SOLUTION: a, b, c, d, e, g, k, n, o, q, t, u, w, x, y, z

PROBLEM: ['r', '1671', 'v', '9019', '7825', '5131', '2251', 'h', '3341', 'v', '9325', 'j', '9493', 'c', '4083', 'v', 'a', '25']

SOLUTION:
a, c, h, j, r, v