#include <iostream>
#include<iomanip>
#include<math.h>



using namespace std;



class point
{
public:
     bool set(double a, double b);
     point();
     point(double x, double y);
     double reflex(int deter);
private:
    double x, y;
};
double distance(double x1, double x2, double y1, double y2);

int main()
{
    point a[3];
    for (int i = 0; i <= 2; i++)
    {
        double x, y;
        cin >> x ;
        cin >> y;

        a[i].set(x, y);
    }
    double dis=0;

    for (int i = 0; i <= 2; i++)
    {
        if (i <2)
        {
            dis=dis+distance(a[i].reflex(1), a[i + 1].reflex(1), a[i].reflex(2), a[i + 1].reflex(2));
            
        }
        if (i == 2)
        {
            dis=dis+distance(a[i].reflex(1), a[0].reflex(1), a[i].reflex(2), a[0].reflex(2));
           
        }
        

    }
    printf("%.2llf", dis);
    return 0;
}



point::point(double a, double b)
{
    x = a;
    y = a;
 }
point::point()
{
    x = 0;
    y = 0;

}
bool point::set(double a, double b)
{
    x = a;
    y = b;
    return true;
}
double point::reflex(int deter)
{
    if (deter == 1)
    {
        return x;
    }
    else
    {
        return y;
    }
}

double distance(double x1,double x2,double y1,double y2)
{
    double aa = (x1 - x2);
    double bb = y1 - y2;
    double result = sqrt(aa * aa + bb * bb);
    return result;
}
  
  

https://picb.cc/image/wbzAzJ 本地运行状况