// 1075.cpp : Defines the entry point for the console application.
//


#include <iostream>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <stdio.h>
using namespace std;
struct point{
    int x;
    int y;
    int z;
    void in(point *);
    double dist(point *,point *);
}Tigran;
void point::in(point *a){
    cin>>a->x;
    cin>>a->y;
    cin>>a->z;
}
double point::dist(point *a, point *b){
    double res_x,res_y,res_z;
    double total_res;
    res_x=((a->x)-(b->x))*((a->x)-(b->x));
    res_y=((a->y)-(b->y))*((a->y)-(b->y));
    res_z=((a->z)-(b->z))*((a->z)-(b->z));
    total_res=sqrt(res_x+res_y+res_z);
    return (total_res);
}
int main(){
    double answer;
    point a,b,c;
    double t;
    double d;
    double x,y,z;
    int R;
    Tigran.in(&a);
    Tigran.in(&b);
    Tigran.in(&c);
    cin>>R;
    x=Tigran.dist(&a,&c);
    y=Tigran.dist(&b,&c);
    z=Tigran.dist(&a,&b);
    if((x*x+z*z<=y*y) && (y*y+z*z<=x*x)){
        answer=z;
    }
    else {
        t=acos((x*x+y*y-z*z)/(2*x*y));
        d=(x*y*sin(t))/z;
        if(d>=(double)R){
            answer=z;
        }
        else {
            answer=sqrt(x*x-R*R)+sqrt(y*y-R*R)+R*(t-acos(R/x)-acos(R/y));
        }
    }
    printf("%0.2f",answer);
    return (0);
}