#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
#include<vector>
struct UF{
	int n;
	vector<int>parent,rank;
	UF(int n_=0):n(n_),parent(n_),rank(n_,1)
	{
		for(int i=0;i<n_;i++)parent[i]=i;
	}
	int find(int a){return parent[a]!=a?parent[a]=find(parent[a]):a;}
	bool same(int a,int b){return find(a)==find(b);}
	bool unite(int a,int b)
	{
		a=find(a),b=find(b);
		if(a==b)return false;
		if(rank[a]<rank[b])
		{
			parent[a]=b;
			rank[b]+=rank[a];
		}
		else
		{
			parent[b]=a;
			rank[a]+=rank[b];
		}
		return true;
	}
	int size(int a){return rank[find(a)];}
};
int N;
int x[1000],y[1000];
main()
{
	cin>>N;
	if(N==0)
	{
		cout<<1<<endl;
		return 0;
	}
	for(int i=0;i<N;i++)cin>>x[i]>>y[i];
	UF uf(N);
	for(int i=0;i<N;i++)for(int j=0;j<N;j++)
	{
		if((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j])<=100)uf.unite(i,j);
	}
	double ans=0;
	for(int i=0;i<N;i++)for(int j=0;j<N;j++)
	{
		if(uf.same(i,j))ans=max(ans,hypot(x[i]-x[j],y[i]-y[j]));
	}
	cout<<fixed<<setprecision(16)<<ans+2<<endl;
}