#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cstdio>
#include <queue>
#include "math.h"
#include <complex>
#include <iomanip>
#include <map>
#define ifor(i,a,b) for (int i=(a);i<(b);i++)
#define rfor(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define rep(i,n) for (int i=0;i<(n);i++)
#define rrep(i,n) for (int i=(n)-1;i>=0;i--)
using namespace std;
typedef long double ld;
typedef long long int  lli;
typedef complex <double> P;
const double eps = 1e-11;
int vex[4]={1,0,-1,0};
int vey[4]={0,1,0,-1};
typedef vector<double> Vec;
typedef vector<int> vec;
typedef vector<Vec> MAT;
typedef vector<vec> mat;
#define UF_MAX 1005
struct UFind{
    int par[UF_MAX];
      int rank[UF_MAX];

        void init(int n){
              rep(i,n){
                      par[i] = i;
                            rank[i] = 0;
                                }
                }
          int find(int x){
                if(par[x]== x){
                        return x;
                            }else {
                                    return par[x]= find(par[x]);
                                        }
                  }
            void unite (int x,int y){
                  x =find(x);
                      y = find(y);
                          if(x==y)return;
                              if(rank[x]<rank[y]){
                                      par[x] = y;
                                          }
                                  else {
                                          par[y] = x;
                                                if(rank[x] == rank[y])rank[x]++;
                                                    }
                                    }
              bool same (int x ,int y){
                    return find(x)==find(y);
                      }
};


lli MOD=1000000007;
int main(){
  double dis[1005][1005];
  UFind f;
  double x[1005],y[1005];
  int N;
  cin >> N;
  rep(i,N)cin>>x[i]>>y[i];
  f.init(N);
  rep(i,N)rep(j,i){
    dis[i][j] = sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
    dis[j][i] = dis[i][j]; 
    if(dis[i][j]<=10)f.unite(i,j);
  }
  double ans = 0;
rep(i,N)rep(j,i){
  if(f.same(i,j))ans=max(ans,dis[i][j]);
}
if(N==0)cout<<1<<endl;
else if(ans<1)cout<<2<<endl;
else printf("%.5f",ans+2);
}