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

#define FOR(x,to) for(x=0;x<to;x++)
class UF {
	public:
	static const int ufmax=1052;
	int ufpar[ufmax],ufrank[ufmax],ufcnt[ufmax];
	UF() { init();}
	void init(){int i; FOR(i,ufmax) { ufpar[i]=i; ufrank[i]=0; ufcnt[i]=1; } }
	int find(int x) {	return (ufpar[x]==x)?(x):(ufpar[x] = find(ufpar[x]));}
	int operator[](int x) {return find(x);}
	int count(int x) {return ufcnt[find(x)];}
	void unite(int x,int y) {
		x = find(x); y = find(y);
		if(x==y) return;
		if(ufrank[x]<ufrank[y]) ufpar[x]=y, ufcnt[y]+=ufcnt[x];
		else {ufpar[y]=x; ufcnt[x]+=ufcnt[y]; if(ufrank[x]==ufrank[y]) ufrank[x]++;}
	}
};

UF uf;
int X[1001], Y[1001];
int dist(int i, int j){
    return pow(X[i]-X[j],2)+pow(Y[i]-Y[j],2);
}
void solve(){
    int N; cin>>N;
    int i,j;
    FOR(i,N){
        cin>>X[i]>>Y[i];
    }

    FOR(i,N) FOR(j,N) if(dist(i, j) <= 100) uf.unite(i,j);
    
    double ma=1;
    if(N)ma=2;
    FOR(i,N) FOR(j,N) if(uf[i]==uf[j]){
        ma=max(ma,2+sqrt(dist(i,j)));
    }
    cout<<fixed<<setprecision(12)<<ma<<endl;
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t=1; //cin>>t;
    for(;t--;) solve();
}