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: ['4371', '9499', 'e', 'w', '9969', '8367', '2897', '1745', 'i', '7049', '9773', 'h', '9649', 'u', '4673', '8513', '8547', 'z', '1995', '7739', '2215', '171', 'c', '7527', '2479', 't', '5223', 'p', '2313', '3243', '2281', 'r', 'c']

SOLUTION: c, e, h, i, p, r, t, u, w, z

PROBLEM: ['d', 'z', '7819', '8211', '3257', '1253', '8141', 'd', '6655', '963']

SOLUTION:
d, z