1 #include<cstdio>
2 #include<cstring>
3 #include<cmath>
4 #include<ctime>
5 #include<iostream>
6 #include<algorithm>
7 #include<queue>
8 #include<set>
9 #define inf (0x7fffffff)
10 #define l(a) ((a)<<1)
11 #define r(a) ((a)<<1|1)
12 #define b(a) (1<<(a))
13 #define T_min (1e-8)
14 #define R (0.9998)
15 #define e (2.718281828459045)
16 #define pi (3.14159265358979323846)
17 #define rep(i,a,b) for(int i=a;i<=(b);i++)
18 #define clr(a) memset(a,0,sizeof(a))
19 typedef long long ll;
20 typedef unsigned long long ull;
21 using namespace std;
22 int readint(){
23 int t=0,f=1;char c=getchar();
24 while(!isdigit(c)){
25 if(c=='-') f=-1;
26 c=getchar();
27 }
28 while(isdigit(c)){
29 t=(t<<3)+(t<<1)+c-'0';
30 c=getchar();
31 }
32 return t*f;
33 }
34 const int maxn=1009;
35 int n;
36 double d[maxn][maxn];
37 struct node{
38 double x,y;
39 inline bool operator<(const node A)const{
40 return x<A.x||(x==A.x&&y<A.y);
41 }
42 }X[maxn];
43 double dis(int u,int v){
44 return sqrt((X[u].x-X[v].x)*(X[u].x-X[v].x)+(X[u].y-X[v].y)*(X[u].y-X[v].y));
45 }
46 int main(){
47 //freopen("#input.txt","r",stdin);
48 //freopen("#output.txt","w",stdout);
49 n=readint();
50 rep(i,1,n){
51 X[i].x=readint();X[i].y=readint();
52 }
53 sort(X+1,X+n+1);
54 //rep(i,1,n) printf("%d %d\n",X[i].x,X[i].y);
55 rep(i,1,n) rep(j,1,n) d[i][j]=1e30;d[1][2]=dis(1,2);
56 rep(j,2,n){
57 rep(i,1,j-1){
58 if(j==i+1){
59 rep(k,1,i-1) d[i][j]=min(d[i][j],d[k][i]+dis(j,k));
60 }else d[i][j]=min(d[i][j],d[i][j-1]+dis(j,j-1));
61 }
62 }
63 double ans=1e30;
64 rep(i,1,n-1) ans=min(ans,d[i][n]+dis(i,n));
65 printf("%.2lf\n",ans);
66 //fclose(stdin);
67 //fclose(stdout);
68 return 0;
69 }
