abstract class Calculator
{
 private $number1;
 private $number2;
 public $result;
 /**
 * @return the $number2
 */
 public function getNumber2() {
 return $this->number2;
 }
 /**
 * @param field_type $number2
 */
 public function setNumber2($number2) {
 $this->number2 = $number2;
 }
 /**
 * @return the $number1
 */
 public function getNumber1() {
 return $this->number1;
 }
 /**
 * @param field_type $number1
 */
 public function setNumber1($number1) {
 $this->number1 = $number1;
 }
 abstract function get_result();
 }
class Add extends Calculator
{
 public function get_result($number1,$number2)
 {
  return $number1+$number2;
 }
}
class Sub extends Calculator
{
 public function get_result($number1,$number2)
 {
  return $number1-$number2;
 }
}
class Mul extends Calculator
{
 public function get_result($number1,$number2)
 {
  return $number1*$number2;
 }
}
class Div extends Calculator
{
 public function get_result($number1,$number2)
 {
  return $number1/$number2;
 }
}
class Factory
{
 public function Building($notes)
 {
  if($notes=="+")
  {
  $add=new Add();
  return $add;
  }
  elseif ($notes=="-")
  {
  $sub=new Sub();
  return $sub;
  }
  elseif($notes=="*")
  {
  $mul=new Mul();
  return $mul;
  }
  else
  {
  $div=new Div();
  return $div;
  }
 }
}