public function power($n, $p)
{
$obj = new Calculator();
if ($n < 0 || $p < 0) {
throw new Exception("n and p should be non-negative");
} else {
if ($p === 0) {
return 1;
}
}
$ans = $obj->power($n, intval($p / 2));
$ans *= $ans;
if ($p % 2 === 1) {
$ans *= $n;
}
return $ans;
}
