class complex {
  double re, im;
public:
  complex (double r, double i) : re {r}, im {i} {}
  complex (double r) : re {r}, im {0.0} {}
  complex () : re {0.0}, im {0.0} {}

  double real () const { return re; }
  void real (double r) { re = r; }
  double imag () const { return im; }
  void imag (double i) { im = i; }

  complex& operator+= (complex z) { re += z.re, im += z.im; return *this; }
  complex& operator-= (complex z) { re -= z.re, im -= z.im; return *this; }
};