#include<bits/stdc++.h>
using namespace std;
#define inf INT_MAX
#define INF LLONG_MAX
#define ll long long
#define ull unsigned long long
#define M (int)(1e9+7)
#define P pair<int,int>
#define PLL pair<ll,ll>
#define FOR(i,m,n) for(int i=(int)m;i<(int)n;i++)
#define RFOR(i,m,n) for(int i=(int)m;i>=(int)n;i--)
#define rep(i,n) FOR(i,0,n)
#define rrep(i,n) RFOR(i,n,0)
#define all(a) a.begin(),a.end()
#define IN(a,n) rep(i,n){ cin>>a[i]; }
const int vx[4] = {0,1,0,-1};
const int vy[4] = {1,0,-1,0};
#define PI 3.14159265
#define F first
#define S second
#define PB push_back
#define EB emplace_back
#define int ll
#define vi vector<int>



template< typename T >
struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }

  operator int() const { return to; }
};

template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WG = vector< Edges< T > >;
using UG = vector< vector< int > >;
template< typename T >
using Matrix = vector< vector< T > >;



struct UnionFind
{

  vector<int> par;
  vector<int> sizes;

  UnionFind(int n) : par(n), sizes(n, 1) {
    rep(i,n) par[i] = i;
  }

  int root(int x) {
    if (x == par[x]) return x;
    return par[x] = root(par[x]); 
  }

  bool unite(int x, int y) {

    x = root(x);
    y = root(y);

    if (x == y) return false;

    if (sizes[x] < sizes[y]) swap(x, y);

    par[y] = x;
    sizes[x] += sizes[y];

    return true;
  }

  bool find(int x,int y){
    return root(x)==root(y);
  }

  int size(int x) {
    return sizes[root(x)];
  }
};


double diameter(P x,P y){
  double d=(x.F-y.F)*(x.F-y.F)+(x.S-y.S)*(x.S-y.S);

  return sqrt(d);
}

signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n;
  cin>>n;
  vector<P> v(n);
  rep(i,n){
    cin>>v[i].F>>v[i].S;
  }

  WG<double> es(n);
  UnionFind uf(n);

  rep(i,n){
    FOR(j,i+1,n){
      double d=diameter(v[i],v[j]);
      if(d<=10){
        uf.unite(i,j);
      }
    }
  }

  double ans=1;

  rep(i,n){
    FOR(j,i,n){
      if(uf.find(i,j)){
        ans=max(ans,diameter(v[i],v[j])+2);
      }
    }
  }

  printf("%.10lf\n",ans);


}