#include <iostream>#include <stdio.h>#include <math.h>using namespace std;#define PI acos(-1)using namespace std;double dis(double x1,double y1,double x2,double y2){return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));}double sum(double x1,double y1,double r1,double x2,double y2,double r2){double s,d,t1,t2,coss1,coss2,o1,o2,ts;d=dis(x1,y1,x2,y2);if(r1<r2){t1=r1;t2=r2;}else {t1=r2;t2=r1;}if(d>=t1+t2||t1==0||t2==0)s=0;elseif(d<=t2-t1)s=PI*t1*t1;else{coss1=(r1*r1+d*d-r2*r2)/(2*r1*d);coss2=(r2*r2+d*d-r1*r1)/(2*r2*d);o1=acos(coss1);o2=acos(coss2);ts=r1*d*(sqrt(1-coss1*coss1));s=r1*r1*o1+r2*r2*o2-ts;}return s;}int main(){double x1,y1,x2,y2,r,r1,r2;double s1,s2,s;while(scanf("%lf%lf%lf%lf%lf%lf%lf",&x1,&y1,&r,&x2,&y2,&r1,&r2)!=EOF){s1=sum(x1,y1,r,x2,y2,r1);s2=sum(x1,y1,r,x2,y2,r2);s=s2-s1;if(s<0)s*=-1;printf("%.3lfn",s);}return 0;}
