#include <iostream>
#include <cmath>
using namespace std;

const double r = acos(0.5) ;

int a1, b1, c1, d1;
int a2, b2, c2, d2;

inline int sq(const int x) {return x * x;}
inline int cu(const int x) {return x*x *x;}

int main (  )
{
	cout.flags(ios::fixed) ;
	cout.precision(4) ;
	
	cin >> a1 >> b1 >> c1 >> d1;
	cin >> a2 >> b2 >> c2 >> d2;
	
	int t= sq (a1-a2) +sq (b1-b2) +sq (c1-c2) ;
	
	if (t <= sq(d2-d1)) cout << cu(min(d1,d2))*r*4;	
	else if (t >=sq (d2+d1)) cout << 0;
	else {
		double x=d1-(sq (d1) - sq (d2) +t) / sqrt (t) / 2;
		double y=d2-(sq (d2) - sq (d1) +t) / sqrt (t) /2;
		cout << (x*x* (3*d1-x) +y*y* (3*d2-y)) *r;
	}
	cout << endl;
	return 0;
}