// includes
#include <bits/stdc++.h>
using namespace std;

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define bit(n) (1LL<<(n))
// functions
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(20);}
} fast_io_;

typedef struct UnionFind_ {
	vector<int> par;
	vector<int> rank_;
  UnionFind_(){}
	explicit UnionFind_(int n): rank_(n, 0) {
    par.resize(n);
    for(int i = 0; i < n; i++)par[i] = i;
	}
	int find(int x) {
    if(par[x] == x)return x;
    else return par[x] = find(par[x]);
	}
	bool same(int x, int y) {
    if(find(x) == find(y))return true;
    else return false;
	}
	bool unite(int x, int y){
    int xp = find(x);
    int yp = find(y);
    if(xp == yp)return false;
    if(rank_[xp] > rank_[yp])par[yp] = xp;
    else if(rank_[xp] < rank_[yp])par[xp] = yp;
    else {
      par[yp] = xp;
      rank_[xp]++;
    }
    return true;
	}
} UnionFind;

vector<int> v[1010];

int main(int argc, char const* argv[])
{
  int n;
  cin >> n;
  if(n == 0){
    cout << 1 << endl;
    return 0;
  }
  vector<ll> x(n), y(n);
  rep(i, n)cin >> x[i] >> y[i];
  UnionFind uf(n);
  rep(i, n){
    rep(j, n){
      ll dis = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
      if(dis <= 100)uf.unite(i, j);
    }
  }
  rep(i, n){
    v[uf.find(i)].pb(i);
  }
  double res = 2;
  rep(i, n){
    rep(j, sz(v[i])){
      FOR(k, j + 1, sz(v[i])){
        double dis = (x[v[i][j]] - x[v[i][k]]) * (x[v[i][j]] - x[v[i][k]]) + (y[v[i][j]] - y[v[i][k]]) * (y[v[i][j]] - y[v[i][k]]);
        dis = sqrt(dis);
        res = max(res, dis + 2.);
      }
    }
  }
  cout << res << endl;
  return 0;
}