#include <bits/stdc++.h>

using namespace std;

class UnionFind {
private:
  int n;
  vector<int> a;
public:
  UnionFind(int n) : n(n), a(n, -1) {}
  int find(int x) {return a[x] < 0 ? x : (a[x] = find(a[x]));}
  bool equal(int x, int y) {return find(x) == find(y);}
  void unite(int x, int y) {
    x = find(x), y = find(y);
    if (x == y) return;
    if (a[x] > a[y]) swap(x, y);
    a[x] += a[y];
    a[y] = x;
    --n;
  }
  int size() {return n;}
  int size(int x) {return -a[find(x)];}
};

int main() {
  int n;
  cin >> n;
  vector<int> x(n), y(n);
  for (int i = 0; i < n; ++i) cin >> x[i] >> y[i];
  UnionFind uf(n);
  for (int i = 0; i < n; ++i) {
    for (int j = i + 1; j < n; ++j) {
      if (pow(x[i] - x[j], 2) + pow(y[i] - y[j], 2) <= 100) uf.unite(i, j);
    }
  }
  double res = (n ? 2 : 1);
  for (int i = 0; i < n; ++i) {
    for (int j = i + 1; j < n; ++j) {
      if (uf.equal(i, j)) res = max(res, hypot(x[i] - x[j], y[i] - y[j]) + 2);
    }
  }
  cout << fixed << setprecision(15) << res << endl;
}