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: ['5431', 'o', 'u', 'l', 'f', 'd', 'r', '1479', '9357', 's', 'v', '6399', 'b', '7937', 't', '8497', 'r', '131', 'h', 'c', 'v', '8879', 'k', 'r', '4687', 'l', '1065', 'r', 'w', 'l', '3305', '461', 'q', 'h', 'b', 'e', 'e', 'w', '5999']

SOLUTION: b, c, d, e, f, h, k, l, o, q, r, s, t, u, v, w

PROBLEM: ['d', 'g', '9019', '9987', '8713', '9513', 'a', '2043', 'd', '5817', 'w', 'd']

SOLUTION: a, d, g, w

PROBLEM: ['e', 'i', '7099', '6837', 't', '9887', '4685', '4355', 'b', '1367', 'h', 'n', 'a', 'p', '9075', '3539', '3361', 'v', '8981', 'g', '8859', 'n', '8591', '5887', '6459', '1091', 'x', 'h']

SOLUTION:
a, b, e, g, h, i, n, p, t, v, x