#include <iostream>
using namespace std;

struct point
{
  double x, y;
};

point operator+(point A, point B);
point operator-(point A, point B);
point operator*(point A, double w);
point operator*(double w, point B);
istream& operator>>(istream &in, point &A);
ostream& operator<<(ostream &out, point A);

double norm(point p);