#include<iostream>
#include<fstream>
#include<cmath>
#include<iomanip>
using namespace std;
int main()
{
  double const Pi=4*atan(1);
  ofstream fout;
  ifstream fin;
  fin.open ("circles.in");
  fout.open ("circles.out");
  int x1,x2,y1,y2,r1,r2,R1,R2;
  fin>> x1 >> y1 >> r1 >> R1 >> x2 >> y2 >> r2 >> R2;
  double S1,S2,S3,final,BR,sr,cS;
  S1=Pi*(R1*R1-r1*r1);
  S2=Pi*(R2*R2-r2*r2);
  if(x1==x2 & y1==y2)
  {
      if(R1>=R2) BR=R1; else BR=R2;
      if(r1<=r2) sr=r1; else sr=r2;
      final=Pi*(BR*BR-sr*sr);
  }
  else final=S1+S2;
  fout<<setprecision(8)<<final;




  fin.close();
  fout.close();
  return 0;
}