#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<string>
#include<cstring>
#include<climits>
#include<functional>
#include<map>
#include<set>
#include<queue>
#include<cmath>
using namespace std;
#define int long long
#define EPS 1e-10

struct Point{
	int x,y;
	Point(){}
	Point(int _x,int _y){
		x=_x; y=_y;
	}
	Point operator-(const Point &a)const{
		return Point(a.x-x,a.y-y);
	}
	int norm(){
		return x*x+y*y;
	}
};

struct Data{
	int n,cost;
	Data(){}
	Data(int _n,int _cost){
		n=_n; cost=_cost;
	}
	bool operator<(const Data &a)const{
		return cost>a.cost;
	}
};

signed main(){
	int N;
	Point P[1000];
	cin>>N;
	for(int i=0;i<N;i++){
		cin>>P[i].x>>P[i].y;
	}
	priority_queue<Data> pq; pq.push(Data(0,0));
	Data pq_c;
	bool memo[1000] = {};
	while(!pq.empty()){
		pq_c = pq.top(); pq.pop();
		if(pq_c.n==N-1){
			printf("%d\n",pq_c.cost*10); return 0;
		}
		if(memo[pq_c.n]) continue;
		memo[pq_c.n] = true;
		for(int i=0;i<N;i++){
			if(pq_c.n==i) continue;
			int cost = (sqrt((P[i]-P[pq_c.n]).norm())-EPS)/10.0;
			cost++;
			pq.push(Data(i,max(pq_c.cost,cost)));
		}
	}
	return 0;
}