#include <cstdio>
#include <iostream>
#include <algorithm>
#include <complex>
using namespace std;
//#define e 2.718281828459
typedef complex<double> point;
typedef point Vector;
double Dot(Vector a,Vector b){return real(conj(a)*b);}
double Cross(Vector a,Vector b){return imag(conj(a)*b); }
Vector Rotate(Vector a,double rad){ return a*exp(point(0,rad));}
point read_point(){
double x,y;
scanf("%lf %lf",&x,&y);
return point(x,y);
}
double length(Ve......
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