text: // Complete the hourglassSum function below.
  #include <iostream>
  
  template <typename Num_t>
  void swap(Num_t& x, Num_t& y) {
    x = x ^ y;
    y = y ^ x;
    x = x ^ y;
  }
  
  int main()
  {
    int a = -1;
    int b = 2;
    swap(a, b);
    std::cout << "a -> " << a << ", b -> " << b << '\n';
    return 0;
  }
  