#include <iostream>
using namespace std;

class Enemy{	
	public:
		virtual void attack()=0;
		
};
class Ninja: public Enemy{
	public:
		void attack()
		{cout << "ninja attack!" <<endl;}
};

class Monster: public Enemy{
	public:
		void attack()
		{cout << "monster attack!" << endl;}
};
int main()
{
	Ninja n;
	Monster m;
	Enemy *enemy1 = &n;
	Enemy *enemy2 = &m;
	enemy1->attack();
	enemy2->attack();
	
}