O> #include <iostream>
 O> using namespace std;

 O> class Complex
 O> {
 O>  double re;
 O>  double im;
 O> public:
 O>  Complex (double re, double im);
 O>  friend ostream& operator<< (ostream& s, const Complex& z);
 O> };

 O> Complex::Complex (double re, double im)
 O> {
 O>  this->re = re;
 O>  this->im = im;
 O> }

 O> ostream& operator<< (ostream& s, const Complex& z)
 O> {
 O>  return s << '(' << z.re << ',' << z.im << ')';
 O> }