#include<bits/stdc++.h>
using namespace std;

#define int long long

typedef long long ll;
typedef pair<int,int>pint;
typedef vector<int>vint;
typedef vector<pint>vpint;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define ln <<endl
#define all(v) (v).begin(),(v).end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
template<class T,class U>void chmin(T &t,U f){if(t>f)t=f;}
template<class T,class U>void chmax(T &t,U f){if(t<f)t=f;}

const double EPS=1e-8;

int N;
int x[1000],y[1000];

int par[1000];
int find(int x){return x==par[x]?x:par[x]=find(par[x]);}
void unite(int x,int y){par[find(y)]=find(x);}
bool same(int x,int y){return find(x)==find(y);}

signed main(){
    cin>>N;
    rep(i,N)cin>>x[i]>>y[i];
    rep(i,N)par[i]=i;

    rep(i,N)rep(j,N){
        double dx=x[i]-x[j],dy=y[i]-y[j];
        double d=dx*dx+dy*dy;
        if(d<100+EPS){
            unite(i,j);
        }
    }

    double ans=1;
    rep(i,N)rep(j,N){
        if(!same(i,j))continue;
        double dx=x[i]-x[j],dy=y[i]-y[j];
        double d=sqrt(dx*dx+dy*dy);
        chmax(ans,d+2);
    }

    printf("%.20f\n",ans);
    return 0;
}