1 #include<iostream>
 2 #include<cstdio>
 3 #include<ctime>
 4 #include<cstdlib>
 5 #include<cmath>
 6 using namespace std;
 7 #define up(i,p,n) for(int i=p;i<=n;i++)
 8 #define down(i,n,p) for(int i=n;i>=p;i--)
 9 namespace OI{
10     const int maxn=20,inf=100000000;
11     int n,a[maxn][2],q[maxn];
12     double d[maxn][maxn];
13     void swa(int i,int j){
14         for(;i<=j;i++,j--){
15             swap(q[i],q[j]);
16         }
17     }
18     double slove(){
19         up(i,1,100){
20             int x=rand()%n+1;
21             int y=rand()%n+1;
22             if(x==n)x=n-1;if(y==n)y=n-1;
23             swap(q[x],q[y]);
24         }
25         up(i,1,n)up(j,i+1,n-1)
26         if(d[q[i]][q[i+1]]+d[q[j-1]][q[j]]>d[q[i]][q[j-1]]+d[q[i+1]][q[j]])swa(i+1,j-1);
27         double t=0;
28         up(i,1,n-1)t+=d[q[i]][q[i+1]];
29         return t;
30     }
31     int squ(int x){return x*x;}
32     void init(){
33         srand(time(0));
34         scanf("%d",&n);n++;
35         up(i,1,n)scanf("%d%d",&a[i][0],&a[i][1]);
36         up(i,1,n)up(j,1,n)
37                 d[i][j]=sqrt(1.0*squ(a[i][0]-a[j][0])+squ(a[j][1]-a[i][1]));
38         //up(i,1,n)up(j,1,n)printf("%d %d %.2lf\n",i,j,d[i][j]);
39         up(i,1,n)q[i]=i;
40         double ans=(double)inf;
41         up(i,1,50000){
42             double t=slove();
43             if(t<ans)ans=t;
44         }
45         printf("%.2lf\n",ans);
46     }
47 }
48 int main(){
49     //freopen("1.in","r",stdin);
50     //freopen("1.out","w",stdout);
51     OI::init();
52     return 0;
53 }