#include <bits/stdc++.h>
using namespace std;
int main(){
  cout << fixed << setprecision(10);
  int N;
  cin >> N;
  vector<int> x(N), y(N);
  for (int i = 0; i < N; i++){
    cin >> x[i] >> y[i];
  }
  vector<vector<int>> E(N);
  for (int i = 0; i < N; i++){
    for (int j = i + 1; j < N; j++){
      if ((x[j] - x[i]) * (x[j] - x[i]) + (y[j] - y[i]) * (y[j] - y[i]) <= 100){
        E[i].push_back(j);
        E[j].push_back(i);
      }
    }
  }
  vector<int> c(N, -1);
  int cnt = 0;
  for (int i = 0; i < N; i++){
    if (c[i] == -1){
      c[i] = cnt;
      queue<int> Q;
      Q.push(i);
      while (!Q.empty()){
        int v = Q.front();
        Q.pop();
        for (int w : E[v]){
          if (c[w] == -1){
            c[w] = cnt;
            Q.push(w);
          }
        }
      }
      cnt++;
    }
  }
  double ans = 1;
  for (int i = 0; i < N; i++){
    for (int j = 0; j < N; j++){
      if (c[i] == c[j]){
        ans = max(ans, hypot(x[j] - x[i], y[j] - y[i]) + 2);
      }
    }
  }
  cout << ans << endl;
}