#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
using namespace std;

struct UnionFind {
    vector<int> data;
    int sz;
    UnionFind(int sz) : data(sz, -1), sz(sz){ }
    bool unionSet(int x, int y) {
        if ((x = root(x)) == (y = root(y))) return false;
        if (data[x] > data[y]) swap(x, y);
        data[x] += data[y]; data[y] = x; sz--;
        return true;
    }
    bool findSet(int x, int y) { return root(x) == root(y); }
    int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
    int size(int x) { return -data[root(x)]; }
    int size() { return sz; }
};

int main() {
  int n;
  cin >> n;
  vector<int> x(n), y(n);
  for (int i = 0; i < n; i++) {
    cin >> x[i] >> y[i];
  }
  if (n == 0) {
    cout << 1 << endl;
    return 0;
  }
  UnionFind uf(n);
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      double d = sqrt(((double)x[i] - x[j])*(x[i] - x[j]) + (y[i] - y[j])*(y[i] - y[j]));
      if (d <= 10) {
        uf.unionSet(i, j);
      }
    }
  }
  double ans = -1;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (uf.findSet(i, j)) {
        double d = sqrt(((double)x[i] - x[j])*(x[i] - x[j]) + (y[i] - y[j])*(y[i] - y[j]));
        ans = max(ans, d);
      }
    }
  }
  ans += 2;
  printf("%.16lf\n", ans);
  return 0;
}