#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>
#include <queue>
using namespace  std;
struct node{
    int index;
    double shortest_path;

   node(int i, double p){
       index = i;
       shortest_path = p;
   }
   bool  operator < (const node & tmp)const {
           return shortest_path > tmp.shortest_path;
   }
};
int main() {
   int N;
   cin >> N;
   vector<pair<int,int>> kordinati;
   for (int i = 0; i < N; i++) {
       int a,b;
       cin >> a >> b;
       kordinati.push_back(make_pair(a,b));
   }
   vector<pair<int,double>> graph [N];
   for (int i = 0; i < N; i++) {
       for (int j = 0; j < N; j++) {
           double D = sqrt((kordinati[j].first - kordinati[i].first) * (kordinati[j].first - kordinati[i].first) +
                           (kordinati[j].second - kordinati[i].second) * (kordinati[j].second - kordinati[i].second));
           if (D<=10){
               graph[i].push_back(make_pair(j,D));
               graph[j].push_back(make_pair(i,D));
           }
         }
       }
   priority_queue<node> pq;
   pq.push(node(0,0));
  
   vector<bool> vistited (N+1, false);
    vector<double> distance(N + 1, 2e9);
    distance[0] = 0;
   while (!pq.empty()){
       node current = pq.top();
       pq.pop();
      
       vistited[current.index] = true;
      
       if(current.index == N-1){
           cout << current.shortest_path << endl;
           break;
       }
       for (int i = 0; i < graph[current.index].size(); i++) {
           int sosed = graph[current.index][i].first;
           double path = graph[current.index][i].second;
          
           if(!vistited[sosed] and current.shortest_path + path < distance[sosed]){
               pq.push(node(sosed,current.shortest_path + path));
               distance[sosed] = current.shortest_path + path;
           }
       }
      
   }
    return 0;
}