bool operator>(Rational& r1, Rational& r2){
  r1.normalize();
  r2.normalize();
  if(r1.getN() > r2.getN()){
    return true;	
  }
  return false;
}
bool operator==(Rational& r1, Rational& r2){
  if( r1.getN() == r2.getN() && r1.getD() == r2.getD() ){
    return true;	
  }
  return false;
}