#include <cassert>// c
#include <ctime>
#include <iostream>// io
#include <iomanip>
#include <fstream>
#include <sstream>
#include <vector>// container
#include <map>
#include <set>
#include <queue>
#include <bitset>
#include <stack>
#include <algorithm>// other
#include <utility>
#include <complex>
#include <numeric>
#include <functional>
#include <random>
#include <regex>

using namespace std;
typedef long long ll;

#define ALL(c) (c).begin(),(c).end()
#define FOR(i,l,r) for(int i=(int)l;i<(int)r;++i)
#define REP(i,n) FOR(i,0,n)
#define FORr(i,l,r) for(int i=(int)r-1;i>=(int)l;--i)
#define REPr(i,n) FORr(i,0,n)
#define EACH(i,c) for(__typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define IN(l,v,r) ((l)<=(v) && (v)<(r))
#define UNIQUE(v) v.erase(unique(ALL(v)),v.end())
//debug
#define DUMP(x)  cerr << #x << " = " << (x)
#define LINE()    cerr<< " (L" << __LINE__ << ")"

template<typename T,typename U> T pmod(T x,U M){return (x%M+M)%M;}

struct UnionFind{
    vector<int> par,rank,ss;int size;
    UnionFind(int n){
        REP(i,n) par.push_back(i);
        rank = vector<int>(n);ss=vector<int>(n,1);size=n;
    }
    int root(int x){
        if(par[x] == x)return x;
        return par[x] = root(par[x]);
    }
    bool same(int x,int y){
        return root(x) == root(y);
    }
    void unite(int x,int y){
        x = root(x);y = root(y);
        if(x==y)return;
        if(rank[x] < rank[y]){
            par[x] = y;ss[y]+=ss[x];
        }else{
            par[y] = x;ss[x]+=ss[y];
        }
        if(rank[x] == rank[y]) rank[x]++;
        size--;
    }
    int getS(int x){
        return ss[root(x)];
    }
};

double EPS=1e-10;

int main(){
	cin.tie(0); ios::sync_with_stdio(false);
	cout <<fixed <<setprecision(20);

	int N;cin >> N;

	vector<double> xs(N),ys(N);
	REP(i,N){
		cin >> xs[i] >> ys[i];
	}

	UnionFind uf(N);
	REP(i,N)REP(j,N)if(hypot(xs[i]-xs[j],ys[i]-ys[j])<=10.0+EPS){
		uf.unite(i, j);
	}

	double Mv=1;
	if(N>0)Mv=2;
	REP(i,N)REP(j,N)if(uf.same(i,j)){
		Mv=max(Mv,hypot(xs[i]-xs[j],ys[i]-ys[j])+2);
	}
	cout << Mv <<endl;
 	return 0;
 }