#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
using ll = long long;
int n;
vector<double> x,y;

double dist(double sx,double sy,double tx,double ty){
	double dx = sx-tx;
	double dy = sy-ty;
	return sqrt(dx*dx+dy*dy);
}

void solve(){
	double ans = 0;
	dsu d(n);
	for(int i = 0;i<n;i++)
		for(int j = i+1;j<n;j++){
			if(dist(x[i],y[i],x[j],y[j])<=10.0+1e-10){
				d.merge(i,j);
			}
		}
	auto vv = d.groups();
	for(auto &v:vv){
		for(int i = 0;i<(int)v.size();i++){
			for(int j = i+1;j<(int)v.size();j++){
				ans = max(dist(x[v[i]],y[v[i]],x[v[j]],y[v[j]]),ans);
			}
		}
	}
	ans += 2;
	if(n==0)ans = 1;
	printf("%.10lf\n",ans);
}

signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cin >>n;
	x = y = vector<double>(n);
	for(int i = 0;i<n;i++)cin >> x[i] >> y[i];
	solve();
}