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: ['1979', 'b', 't', '1101', '7953', '2451', '7539', '6833', 'u', '49']

SOLUTION: b, t, u

PROBLEM: ['n', 't', '2901', '9697', 'a', 'j', 'x', 'a', '4437', '2255', '2177', 's', '3173', 'j', 't', '5713', '4091', '4253', '5553', 'i', '4533', 'i', 'e', '6899', 's', '3541', '2139', '2705', 'm', 'u']

SOLUTION: a, e, i, j, m, n, s, t, u, x

PROBLEM: ['3095', '719', '555', 'm', 'e', '289', 'u', '2047', 'h', '5797', '1445', 'f', 'b', 'n', 'p', 'd', '7081', 'x', 'f', 'j', '2239', '3555', 'h', 'i', '4127', '2949', 'w', 'r', 'v', 'n', 'o', 'c', 'f', '5925', '6215', '5477', 'a', 'f', 'e', '5263']

SOLUTION:
a, b, c, d, e, f, h, i, j, m, n, o, p, r, u, v, w, x