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: ['j', 'y', '9907', 'a', '5715', 'l', '9817', '1949', '2697', '2255', '9571', '8957', '9329', '6055', 'z', 'q', '1185', '4593']

SOLUTION: a, j, l, q, y, z

PROBLEM: ['8235', 't', '1695', '9899', '3633', 't', '1823', 'r', 'x']

SOLUTION: r, t, x

PROBLEM: ['1235', '2193', 'c', 'f', 's', 'a', 'b', 'n', 'c', 'g', '1711', 'n', 'q', 'k', '3913', '8491', '4379', '7887', '665', 't', 'p', '4033', 'c', 'k', 'k', 'm', '3805', 'h', 'r', 'k', '6803', 'i', '3469', 'q', '3365', '3987', '303', '3211', '1039', '3015', 'q', 'g', '3599']

SOLUTION:
a, b, c, f, g, h, i, k, m, n, p, q, r, s, t