#include <queue>
#include <iostream>
#include <vector>
#include <cstring>
#include <iostream>
#include <bits/stdc++.h>
using namespace std;





struct node{
        int indx;
        double dis;
        node()
        {




       }
        node(int indx1, double dis1)
        {
            indx=indx1;
            dis=dis1;
        }
        bool operator < (const node &tmp) const{
            return dis>tmp.dis;
        }
    };
int main()
{
    int n;
    cin>>n;
    vector < pair<int,int> > v;
    int x,y;
    for(int i=0;i<n;i++)
    {
        cin>>x>>y;
        v.push_back(make_pair(x,y));
    }
    vector < pair<int, double> > g[n];




   vector<bool> visited(n,false);
    vector<double> dis(n,2e9);
    for(int i=0;i<n;i++)
    {
        for(int j=i;j<n;j++)
        {
            double d=sqrt(((v[j].first-v[i].first) * (v[j].first-v[i].first))+((v[j].second-v[i].second)*(v[j].second-v[i].second)));
            if(d<=10)
                g[i].push_back(make_pair(j,d));
        }
    }
    dis[0]=0;
    priority_queue<node> pq;
    pq.push(node(0,0));




   while(!pq.empty())
    {
        node c=pq.top();

        pq.pop();


       if(visited[c.indx])
        {
            continue;
        }
        visited[c.indx]=true;
        for(int i=0;i<g[c.indx].size();i++)
        {
            int s=g[c.indx][i].first;
            double t=g[c.indx][i].second;




           if(!visited[s] && c.dis+t<dis[s])
            {
                pq.push(node(s,c.dis+t));
                dis[s]=c.dis+t;
            }
        }
    }
    cout<<dis[n-1]<<endl;
    return 0;
}