sub lcs{
	our %subs = ();
	my $n = @_;
	shift =~ m[^.*(.+)(?{ $subs{ $^N }++ })(?!)] while @_;
	my @subs = sort{ length $b <=> length $a } 
                 grep{ $subs{ $_ } == $n } keys %subs;

	return wantarray ? @subs : $subs[ 0 ];
}