#include <string>
#include <iostream>

class Output
{
public:
	void output(const std::string & str)
	{
		std::cout << str << std::endl;
	}
};

class World
{
	Output & out;
public:
	World(Output & out) : out(out) { }
	void output(const std::string & str)
	{
		out.output(str + " world!");
	}
};

class Hello
{
	World & world;
public:
	Hello(World & world) : world(world) { }
	void output()
	{
		world.output("Hello");
	}
};

void hello_world(Hello & hello)
{
	hello.output();
}

int main()
{
	Output output;
	World world(output);
	Hello hello(world);
	hello_world(hello);
	return 0;
}