#include<iostream>

 #include<cstdio>

 #include<cstring>

 #include<cmath>

 #include<cstdlib>

 #include<algorithm>

 #define inf 0x7fffffff

 #define PI 3.141592654

 #define exp 1e-10

 using namespace std;

 struct Point

 {

     double x,y;

     Point (double x=,double y=):x(x),y(y){}

     friend bool operator < (Point A,Point B)

     {

         if (A.x != B.x) return A.x < B.x;

         return A.y<B.y;

     }

 }an[];

 typedef Point Vector;

 Vector operator + (Vector A,Vector B) {return Vector(A.x+B.x , A.y+B.y); }

 Vector operator - (Vector A,Vector B) {return Vector(A.x-B.x , A.y-B.y); }

 int dcmp(double x)

 {

     if (fabs(x)<exp) return ;

     else return x< ? - : ;

 }

 double cross(Vector A,Vector B)

 {

     return A.x*B.y-B.x*A.y;

 }

 int ConvexHull(Point *p,int n,Point *ch)

 {

     sort(p,p+n);

     int m=;

     for (int i= ;i<n ;i++)

     {

         while (m> && dcmp(cross(ch[m-]-ch[m-] , p[i]-ch[m-]))<=) m--;

         ch[m++]=p[i];

     }

     int k=m;

     for (int i=n- ;i>= ;i--)

     {

         while (m>k && dcmp(cross(ch[m-]-ch[m-] , p[i]-ch[m-]))<=) m--;

         ch[m++]=p[i];

     }

     ch[m++]=ch[];

     if (n>) m--;

     return m;

 }

 double dis(Point a,Point b)

 {

     return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));

 }

 int main()

 {

     int n;

     while (cin>>n,n)

     {

         for (int i= ;i<n ;i++)

         scanf("%lf%lf",&an[i].x,&an[i].y);

         if (n==) {printf("0.00\n");continue;}

         else if (n==) {printf("%.2f\n",dis(an[],an[]));continue;}

         Point bn[];

         int m=ConvexHull(an,n,bn);

         double sum=;

         for (int i= ;i<m ;i++)

         {

             sum += dis(bn[i],bn[i+]);

         }

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

     }

     return ;

 }