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: ['g', 'u', 'q', '1375', '9491', 't', 'w', 'c', 'v', 'y', '3169', '1607']

SOLUTION: c, g, q, t, u, v, w, y

PROBLEM: ['u', 'o', 'b', 'b', '5873', 'w', 'v', '4171', '7957', '3501', '2563', 'l', 'q']

SOLUTION: b, l, o, q, u, v, w

PROBLEM: ['71', 'd', '4067', 't', 'k', 'w', '3301', '7609', '1901', 'd', '1259', 'n', 'z', 'f', 'c', '4655', '2455', '3615', '3503', '1027', 'r', '2457', 'q', '5073', '1801', 'u', 'b', 'u', '9007', '7805', '967', 'm', 'o', '9755', 'z', '7629']

SOLUTION:
b, c, d, f, k, m, n, o, q, r, t, u, w, z