#include <iostream> 
using namespace std;

int main()
{
  int person1_age = 15;
  int& person2_age = person1_age;

  cout << "Person 1 and Person 2 are twins." << endl;

  cout << "Person 1 is " << person1_age << endl;
  cout << "Person 2 is " << person2_age << endl;

  cout << "Happy birthday person 1 & person 2!" << endl;

  person1_age += 1;

  cout << "Person 1 is now " << person1_age << endl;
  cout << "Person 2 is now " << person2_age << endl;

  return 0;
}