sub clear_totals {
    $_[0]->walk_down({ callback => sub {
        my $node = shift;
        if ($node->daughters) {
            $node->budget(0);
            $node->employees(0);
        }
    }})
}

sub sum_up {
    $_[0]->walk_down({ callbackback=> sub {
        my $node = shift;
        return 1 unless $node->mother;
        $node->mother->attributes->{employees}
            += $node->attributes->{employees};
        $node->mother->attributes->{budget}
            += $node->attributes->{budget};
    }});
}

sub print_wealth {
    $_[0]->walk_down({callback=> sub {
        my $node = shift;
        printf "%s%.7s\templ: %2d  budget: %8d\n",
            "  " x $_[0]->{_depth},
            $node->name, $node->employees,
            $node->budget
    }, _depth => 0 });
}