#include <bits/stdc++.h>
#define EPS 1e-9
#define INF 1070000000LL
#define MOD 1000000007LL
#define fir first
#define foreach(it,X) for(auto it=(X).begin();it!=(X).end();it++)
#define numa(x,a) for(auto x: a)
#define ite iterator
#define mp make_pair
#define rep(i,n) rep2(i,0,n)
#define rep2(i,m,n) for(int i=m;i<(n);i++)
#define pb push_back
#define pf push_front
#define sec second
#define sz(x) ((int)(x).size())
#define ALL( c ) (c).begin(), (c).end()
#define gcd(a,b) __gcd(a,b)
#define mem(x,n) memset(x,n,sizeof(x))
#define endl "\n"
using namespace std;
template <int POS, class TUPLE> void deploy(std::ostream &os, const TUPLE &tuple){}
template <int POS, class TUPLE, class H, class ...Ts> void deploy(std::ostream &os, const TUPLE &t){ os << (POS == 0 ? "" : ", ") << get<POS>(t); deploy<POS + 1, TUPLE, Ts...>(os, t); }
template <class T,class U> std::ostream& operator<<(std::ostream &os, std::pair<T,U> &p){ os << "(" << p.first <<", " << p.second <<")";return os; }
template <class T> std::ostream& operator<<(std::ostream &os, std::vector<T> &v){ int remain = v.size(); os << "{"; for(auto e: v) os << e << (--remain == 0 ? "}" : ", "); return os; }
template <class T> std::ostream& operator<<(std::ostream &os, std::set<T> &v){ int remain = v.size(); os << "{"; for(auto e: v) os << e << (--remain == 0 ? "}" : ", "); return os; }
template <class T, class K> std::ostream& operator<<(std::ostream &os, std::map<T, K> &mp){ int remain = mp.size(); os << "{"; for(auto e: mp) os << "(" << e.first << " -> " << e.second << ")" << (--remain == 0 ? "}" : ", "); return os; }
#define DEBUG1(var0) { std::cerr << (#var0) << "=" << (var0) << endl; }
#define DEBUG2(var0, var1) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG1(var1); }
#define DEBUG3(var0, var1, var2) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG2(var1,var2); }
#define DEBUG4(var0, var1, var2, var3) { std::cerr << (#var0) << "=" << (var0) << ", ";DEBUG3(var1,var2,var3); }
using ll = long long;

int N;
pair <int,int> XY[1010];
vector <int> edge[1010];
double dist[1010][1010];
bool OK(int i,int j){
  dist[i][j] = sqrt(pow(XY[i].fir - XY[j].fir,2) + pow(XY[i].sec - XY[j].sec,2));
  return dist[i][j] <= 10;
}
bool used[1010];



//Union-find木
#define MAX_N 1010
int par[MAX_N];
int myrank[MAX_N];

void init(int n){//要素初期化
  rep(i,n){
    par[i] = i;
    myrank[i] = 0;
  }
}

int find(int x){//木の根を求める
  if(par[x] == x){
    return x;
  }else{
    return par[x] = find(par[x]);
  }
}

void unite(int x,int y){//xとyの属する集合を併合
  x = find(x);
  y = find(y);
  if(x == y){
    return;
  }
  if(myrank[x] < myrank[y]){
    par[x] = y;
  }else{
    par[y] = x;
    if(myrank[x] == myrank[y]){
      myrank[x] += 1;
    }
  }
}

bool same(int x,int y){//x,yが同じ集合に属するか否か
  return find(x) == find(y);
}

void dfs(int v,int root){
  used[v] = true;
  unite(v,root);
  numa(x,edge[v]){
    if(!used[x]){
      dfs(x,root);
    }
  }
}


int main()
{
  cin.tie(0);
  ios_base::sync_with_stdio(0);
  cin >> N;
  if(N == 0){
    cout << fixed << setprecision(10) << 1 << endl;
    return 0;
  }
  rep(i,N){
    int x,y;
    cin >> x >> y;
    XY[i] = mp(x,y);
  }
  rep(i,N){
    rep2(j,i+1,N){
      if(OK(i,j)){
        edge[i].pb(j);edge[j].pb(i);
      }
    }
  }
  init(MAX_N-1);
  rep(i,N){
    if(!used[i]){
      dfs(i,i);
    }
  }
  double ans = 0;
  rep(i,N){
    rep2(j,i+1,N){
      if(same(i,j)){
        ans = max(ans,dist[i][j]);
      }
    }
  }
  cout << fixed << setprecision(10) <<ans + 2 << endl;
  
  return 0;
}