#include<cstdio> #include<cstring> #include<algorithm> #include<cmath> #include<complex> #include<vector> #include<deque> using namespace std; typedef long long LL; #define INF 0x7fffffff #define zero(x) (((x)>0?(x):(-x))<eps) const double eps=1e-8; const double pi=acos(-1.0); int dcmp(double x) { return x<-eps?-1:x>eps?1:0;} double sqr(double x) { return x*x;} double mysqrt(double n) { return sqrt(max(0.0,n));} struct point { double x,y; point() {}; point(double a,double b):x(a),y(b) {}; }; typedef point Vector; //向量-向量 Vector operator -(const Vector &a, const Vector &b) {return Vector(a.x-b.x, a.y-b.y);} //向量+向量 Vector operator +(const Vector &a, const Vector &b) {return Vector(a.x+b.x, a.y+b.y);} //向量*常数 Vector operator *(const double &a, const Vector &b) {return Vector(a*b.x, a*b.y);} Vector operator *(const Vector &a, const double &b) {return Vector(a.x*b, a.y*b);} Vector operator /(const Vector &a, const double &b) {return Vector(a.x/b,a.y/b);} //向量*向量 Dot double dot(const Vector &a,const Vector &b) {return a.x*b.x+a.y*b.y;} //向量X向量 double cross(const Vector &a,const Vector &b) {return a.x*b.y-a.y*b.x;} //向量==向量 bool isequal(const Vector &a,const Vector &b) {return dcmp(a.x-b.x)==0&&dcmp(a.y-b.y)==0;} double Area(vector<point> p) { int n=p.size(); double area = 0; for(int i=1; i<n-1; ++i) area += cross(p[i]-p[0], p[i+1]-p[0]); return fabs(area/2); } //struct halfplane //{ // point a,b; // halfplane() {}; // halfplane(point a,point b):a(a),b(b) {}; //}; typedef pair<point,point> halfplane; inline double satisfy(point a,halfplane p) { return dcmp(cross(a-p.first,p.second-p.first))<=0; } point crosspoint(const halfplane &a,const halfplane &b) { double k=cross(b.first-b.second,a.first-b.second); k=k/(k-cross(b.first-b.second,a.second-b.second)); return a.first+(a.second-a.first)*(k); } double arg(point p) { return arg(complex<double>(p.x,p.y)); } bool cmp(const halfplane &a,const halfplane &b) { int res=dcmp(arg(a.second-a.first)-arg(b.second-b.first)); return res==0? satisfy(a.first,b):res<0; } vector<point> halfplaneIntersection(vector<halfplane> v) { sort(v.begin(),v.end(),cmp); deque<halfplane> q; deque<point> ans; q.push_back(v[0]); for(int i=1; i<v.size(); ++i) { if(dcmp(arg(v[i].second-v[i].first)-arg(v[i-1].second-v[i-1].first))==0) { continue; } while(ans.size()>0&&!satisfy(ans.back(),v[i])) { ans.pop_back(); q.pop_back(); } while(ans.size()>0&&!satisfy(ans.front(),v[i])) { ans.pop_front(); q.pop_front(); } ans.push_back(crosspoint(q.back(),v[i])); q.push_back(v[i]); } while(ans.size()>0&&!satisfy(ans.back(),q.front())) { ans.pop_back(); q.pop_back(); } while(ans.size()>0&&!satisfy(ans.front(),q.back())) { ans.pop_front(); q.pop_front(); } ans.push_back(crosspoint(q.back(),q.front())); return vector<point>(ans.begin(),ans.end()); } vector<halfplane> hp; vector<point> ans; point p[100],q[100]; int main() { double x1,Y1,x2,Y2; double x3,Y3,x4,Y4; while(scanf("%lf %lf %lf %lf",&x1,&Y1,&x2,&Y2)!=EOF) { scanf("%lf %lf %lf %lf",&x3,&Y3,&x4,&Y4); p[0]=point(x1,Y1); p[1]=point(x2,Y1); p[2]=point(x1,Y2); hp.clear(); //要逆时针插入 if(x1>x2&&Y1>Y2) { hp.push_back(halfplane(p[0],p[1])); hp.push_back(halfplane(p[1],p[2])); hp.push_back(halfplane(p[2],p[0])); } else if(x1>x2&&Y1<Y2) { hp.push_back(halfplane(p[1],p[0])); hp.push_back(halfplane(p[0],p[2])); hp.push_back(halfplane(p[2],p[1])); } else if(x1<x2&&Y1>Y2) { hp.push_back(halfplane(p[0],p[2])); hp.push_back(halfplane(p[2],p[1])); hp.push_back(halfplane(p[1],p[0])); } else if(x1<x2&&Y1<Y2) { hp.push_back(halfplane(p[0],p[1])); hp.push_back(halfplane(p[1],p[2])); hp.push_back(halfplane(p[2],p[0])); } q[0]=point(x3,Y3); q[1]=point(x4,Y3); q[2]=point(x4,Y4); q[3]=point(x3,Y4); hp.push_back(halfplane(q[0],q[1])); hp.push_back(halfplane(q[1],q[2])); hp.push_back(halfplane(q[2],q[3])); hp.push_back(halfplane(q[3],q[0])); ans =halfplaneIntersection(hp); printf("%.8f ",Area(ans)); } return 0; }