#include <iostream>
#include <cstdlib>
#include "atom.h"
using namespace std;

int main()
{
	const hydrogen h;
	const helium   he;
	const oxygen   o;

	cout <<  "H belongs to period " << hydrogen::period() << ".\n";
	cout << "He belongs to period " <<   helium::period() << ".\n";
	cout <<  "O belongs to period " <<   oxygen::period() << ".\n";

	return EXIT_SUCCESS;
}