#include <fstream>
#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

double PI = 3.1415926;

double interception(int x1, int x2, int y1, int y2, int R1, int R2)
{
    double result = 0;
    double d = sqrt((x2 - x1)*(x2-x1)+(y2-y1)*(y2-y1)) / 2;
    double angle2 = 2*acos(d/R2)*180/PI;
    result += R2*R2/2*(angle2*PI/180 - sin(angle2*PI/180));
    double angle1 = 2*acos(d/R1)*180/PI;
    result += R1*R1/2*(angle1*PI/180 - sin(angle1*PI/180));
    return result;
}

int main()
{
    ifstream fin;
    fin.open("circles.in");
    int x1, x2, y1, y2, r1, r2, R1, R2;
    fin >> x1 >> y1 >> r1 >> R1
        >> x2 >> y2 >> r2 >> R2;

    double area1 = PI * R1 * R1 - PI * r1 * r1;
    double area2 = PI * R2 * R2 - PI * r2 * r2;
    double result = area1 + area2;
    if(sqrt((x2 - x1)*(x2 - x1) + (y2 - y1)*(y2 - y1)) < R1 + R2)
    {
        result -= interception(x1, x2, y1, y2, R1, R2);
        double d = sqrt((x2 - x1)*(x2-x1)+(y2-y1)*(y2-y1));
        if(d - R2 < r1)
        {
            result += 2*interception(x1, x2, y1, y2, r1, R2);
        }

        if(d - R1 < r2)
        {
            result += 2*interception(x1, x2, y1, y2, R1, r2);
        }
    }
    ofstream fout;
    fout.open("circles.out");
    fout << fixed << setprecision(6) << result  << endl;

    return 0;
}