public function multiplicationLarge()
 {
     $a = new BigInt('36486872398567981638843143228254546051651870');
     $b = new BigInt('50602640980469152653015');
     $r = new BigInt('1846332104484924953979619544386780054125593365543499568033685888050');
     $this->assertEquals($r, $a->multiply($b));
 }