#include <iostream>
#include <vector>
#include <queue>
#include <cmath>
using namespace std;
struct node{
int index;
double distance;
node(){

}
node(int _index, double _distance){
index=_index;
distance=_distance;
}
bool operator <(const node& temp)const{
return distance>temp.distance;
}
};

int main()
{
int n;
cin>>n;
vector<pair<int, double>>v;
vector<pair<int, double>>graph[n];
for(int x=0; x<n; x++){
    int a, b;
    cin>>a;
    cin>>b;
    v.push_back(make_pair(a, b));
}
for(int y=0; y<v.size(); y++){
    for(int u=0; u<v.size(); u++){
        double d=sqrt((v[y].first-v[u].first)*(v[y].first-v[u].first)+(v[u].second-v[y].second)*(v[u].second-v[y].second));
        if(d<=10){
         graph[y].push_back(make_pair(u, d));
        }
    }
}
int s, e;
s=0;
e=n-1;
    priority_queue<node>pq;
    pq.push(node(s, 0));
    bool visited [n];
    double distance[n];
    for(int h=0; h<n; h++){
        visited[h]=false;
        distance[h]=200000000;
    }
    distance[0] = 0;
    while(!pq.empty()){
    node c=pq.top();
    pq.pop();
    visited[c.index]=true;
    for(int k=0; k<graph[c.index].size(); k++){
    int sosed=graph[c.index][k].first;
    double d1=graph[c.index][k].second;
    if((visited[sosed]==false)and(c.distance+d1<distance[sosed])){
     distance[sosed]=c.distance+d1;
     pq.push(node(sosed, distance[sosed]));
    }
    }
    }
    cout<<distance[n-1];
    return 0;
}