/* -*- coding: utf-8 -*-
 *
 * 94.cc: No.94 圏外です。(EASY) - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 1000;

/* typedef */

typedef vector<int> vi;
typedef queue<int> qi;

/* global variables */

int xs[MAX_N], ys[MAX_N];
vi nbrs[MAX_N];
bool used[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> xs[i] >> ys[i];

  for (int i = 0; i < n; i++)
    for (int j = i + 1; j < n; j++) {
      int dx = xs[j] - xs[i], dy = ys[j] - ys[i];
      if (dx * dx + dy * dy <= 10 * 10) {
	nbrs[i].push_back(j);
	nbrs[j].push_back(i);
      }
    }

  if (n == 0) {
    printf("%.9lf\n", 1.0);
    return 0;
  }
  
  int maxd2 = 0;
  
  for (int i = 0; i < n; i++)
    if (! used[i]) {
      used[i] = true;
      qi q;
      q.push(i);
      vi ps;
      ps.push_back(i);

      while (! q.empty()) {
	int u = q.front(); q.pop();
	vi &nbru = nbrs[u];
	for (vi::iterator vit = nbru.begin(); vit != nbru.end(); vit++) {
	  int &v = *vit;
	  if (! used[v]) {
	    used[v] = true;
	    q.push(v);
	    ps.push_back(v);
	  }
	}
      }

      int pn = ps.size();
      for (int j = 0; j < pn; j++) {
	int xj = xs[ps[j]], yj = ys[ps[j]];
	for (int k = j + 1; k < pn; k++) {
	  int xk = xs[ps[k]], yk = ys[ps[k]];
	  int dx = xk - xj, dy = yk - yj;
	  int d2 = dx * dx + dy * dy;
	  if (maxd2 < d2) maxd2 = d2;
	}
      }
    }

  printf("%.9lf\n", sqrt((double)maxd2) + 2.0);
  return 0;
}