binarySearch(arr, x, low, high)
           if low > high
               return False 
   
           else
               mid = (low + high) / 2 
                   if x == arr[mid]
                   return mid
       
               else if x > arr[mid]        // x is on the right side
                   return binarySearch(arr, x, mid + 1, high)
               
               else                        // x is on the left side
                   return binarySearch(arr, x, low, mid - 1);
