interface Either {}
class Left implements Either {
    private $a;

    public function __construct($a) {
        $this->a = $a;
 
    }
    public function patternMatched(callable $fn) {
        return $fn($this->a);
    }
}
class Right implements Either {
    private $b;

    public function __construct($b) {
        $this->b = $b;
 
    }
    public function patternMatched(callable $fn) {
        return $fn($this->b);
    }
}