#include<cmath>
#include<iostream>
#include<cstdio>
#include<complex>

using namespace std;

struct xyz{
  double x, y, z;
};

typedef complex<double> xy;

xy tang(xy p, double r)
{
  double theta = arg(p);
  double l = abs(p);
  theta -= asin(r / l);
  double d = sqrt(l * l - r * r);

  return polar(d, theta);
}

double tangd(xy p, double r)
{
  double theta = arg(p);
  double l = abs(p);
  theta -= asin(r / l);
  double d = sqrt(l * l - r * r);

  return d;
}

double distance (xyz &p1, xyz &p2)
{
  return sqrt((p2.x - p1.x) * (p2.x - p1.x) +
              (p2.y - p1.y) * (p2.y - p1.y) +
              (p2.z - p1.z) * (p2.z - p1.z));
}

void main(void)
{
  xyz a, b, c;
  double r;

  cin >> a.x >> a.y >> a.z;
  cin >> b.x >> b.y >> b.z;
  cin >> c.x >> c.y >> c.z;
  cin >> r;

  double ab = distance(a, b);
//  cout << ab << endl;
  double ac = distance(a, c);
//  cout << ac << endl;
  double bc = distance(b, c);
//  cout << bc << endl;

  double costheta = (ac * ac + ab * ab - bc * bc) / (2. * ac * ab);
//  cout << costheta << endl;
  double cx = ac * costheta;
  double h = sqrt(ac * ac - cx * cx);
//  cout << h << endl;

  if( h >= r || cx >= ab || cx <= 0. || ab <= 0.01) {
    printf("%.2f\n", ab);
    return;
  }

  xy ccenter(cx, h);

  xy tanleft = tang(ccenter, r);
  double leftd = tangd(ccenter, r);
//  cout << "ld" << leftd << endl;

  xy tanright = conj(xy(ab, 0) - tang(xy(ab - cx, h), r));
  double rightd = tangd(xy(ab - cx, h), r);
//  cout << "rd" << rightd << endl;

//  cout << arg(tanleft - ccenter) << ":" << arg(tanright - ccenter) << endl;
//  cout << fabs(arg(tanleft - ccenter) - arg(tanright - ccenter)) << endl;
  double res = fabs(arg(tanleft - ccenter) * r - arg(tanright - ccenter) * r) + leftd + rightd;

  printf("%.2f\n", res);

  return;
}