#include <cstdio>
#include <cmath>
#include <algorithm>
#define eps 1e-5
#define INF 1e20
using namespace std;
const double pi=acos(-1.0);
inline double sq(double x) { return x*x; }
struct Point {
double x,y;
Point() {}
Point(double _x,double _y):x(_x),y(_y) {}
void scan() { scanf("%lf%lf",&x,&y); }
Point operator - (const Point& rhs) const {
return Point(x-rhs.x,y-rhs.y);
}