#!/usr/bin/env python3

"""Convert time between zones"""

from sys import argv
import re


def get_int(prompt, argnum):
    """Gets number

    If var is a number, return it. Else, get number from input until it
    doesn't fail.
    """
    try:
        number = int(argv[argnum])
    except (ValueError, IndexError):
        number = None
        while number is None:
            try:
                number = int(input(prompt))
            except ValueError:
                number = None
    return number


# They all return a value. Pylint is wrong
# pylint: disable=inconsistent-return-statements
def get_time(prompt, argnum):
    """Gets a time, in the same vein as get_int"""
    time_regex = re.compile("([01]?[0-9]|2[0-3]):[0-5][0-9]")
    try:
        if re.match(time_regex, argv[argnum]):
            return argv[argnum]
    except (ValueError, IndexError):
        time_inp = ""
        while not re.match(time_regex, time_inp):
            time_inp = input(prompt)
        return time_inp


tz_from = get_int("From: ", 1)
tz_to = get_int("To: ", 2)
conv_time = get_time("Time: ", 3).split(':')

hours = conv_time[0]
minutes = conv_time[1]

leading_zero = len(hours) == 2

# `hours' is NOT a constant
# pylint: disable=invalid-name
hours = str((int(hours) + abs(tz_from - tz_to)) % 24)
if leading_zero and int(hours) < 10:
    hours = "0" + hours

print(f"{hours}:{minutes}")