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

using namespace std;

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

point sub( point a, point b ) {
  point ret;
  ret.x = a.x - b.x;
  ret.y = a.y - b.y;
  ret.z = a.z - b.z;
  return ret;
}

double dot_product( point a, point b ) {
  return a.x * b.x + a.y * b.y + a.z * b.z;
}

double len( point a, point b ) {
  return sqrt( dot_product( sub( a, b ), sub( a, b ) ) );
}

int main( void )
{
  point a, b, c;
  double R;
  cin >> a.x >> a.y >> a.z >> b.x >> b.y >> b.z >> c.x >> c.y >> c.z >> R;

  double direct_length = len( a, b );
  if ( direct_length == 0.00 ) {
    printf( "0.00\n" );
    return 0;
  }

  double k = dot_product( sub( a, b ), sub( c, b ) ) / dot_product( sub( a, b ), sub( a, b ) );
  double length;
  if ( k <= 0.0 || k >= 1.0 ) {
    length = direct_length;

  } else {
    point h;
    double r;
    
    h.x = a.x * k + b.x * ( 1 - k );
    h.y = a.y * k + b.y * ( 1 - k );
    h.z = a.z * k + b.z * ( 1 - k );

    r = len( h, c );
    
    if ( r >= R ) {
      length = direct_length;
    } else {
      double AC = len( a, c );
      double BC = len( b, c );

      double theta_aR = ( R >= AC ) ? 0 : acos( R / AC );
      double theta_bR = ( R >= BC ) ? 0 : acos( R / BC );
      double theta_ar = ( r >= AC ) ? 0 : acos( r / AC );
      double theta_br = ( r >= BC ) ? 0 : acos( r / BC );

      length = R * tan( theta_aR ) + R * tan( theta_bR ) + R * ( theta_ar + theta_br - theta_aR - theta_bR );
    }
  }

  // printf( "%d.%02d\n", ( int ) floor( length ), ( ( int ) floor( length * 100 + 0.5 ) ) % 100 ) ;
  printf( "%.02f\n", length );
  return 0;
}