#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <cmath>
using namespace std;
struct node
{
    int idx;
    double dis;
    node(int _idx, double _dis)
    {
        idx=_idx;
        dis=_dis;
    }
    bool operator < (const node &tmp) const
    {
        return dis> tmp.dis;
    }
};
int main()
{
    int n,x,y;
    cin>>n;
    vector<pair<int,int>>v;
    vector<pair<int,double>>par[n+5];
    for(int i=0;i<n;i++)
    {
        cin>>x>>y;
        v.push_back({x,y});
    }
    for(int i=0;i<n;i++)
    {
        for(int j=0;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)
            {
                par[i].push_back({j,d});
            }
        }
    }
    priority_queue<node>Q;
    Q.push(node(0,0));
    double d[n+5];
    bool vis[n];
    for(int j=0;j<n;j++)
    {
        d[j]=2e9;
        vis[j]=false;
    }
    d[0]=0;
    while(!Q.empty())
    {
        node teme=Q.top();
        Q.pop();
        vis[teme.idx]=true;
        for(int i=0;i<par[teme.idx].size();i++)
        {
            int sosed=par[teme.idx][i].first;
            double r=par[teme.idx][i].second;
            if(!vis[sosed] && teme.dis + r < d[sosed])
            {
                d[sosed]=teme.dis + r;
                Q.push(node(sosed,d[sosed]));
            }
        }
    }
    cout<<d[n-1];
    return 0;
}