#!/usr/bin/perl

use strict;
use warnings;

my $year = shift @ARGV;
print is_leap_year($year) ? "$year is a leap year.\n" : "$year isn't a leap year.\n";
exit;

sub is_leap_year {
    my $year = shift;
    return ($year % 400 == 0 or ($year % 100 != 0 and $year % 4 ==0)) ? 1 : 0;
}