#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
#include <iomanip>
using namespace std;

#define REP(i,s,e) for (i = s; i <= e; i++)
#define rep(i,n) REP (i,0,(int)(n)-1)
#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP (i,(int)(n)-1,0)
#define INF (int)1e8
#define MOD (int)(1e9+7)

typedef long long ll;

int n;
int par[1000];

void init() {
    int i;
    rep (i,n) par[i] = i;
}

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

void unite(int x, int y) {
    par[find(x)] = find(y);
}

int dist2(int x1, int y1, int x2, int y2) {
    return (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
}

double dist(pair<int,int> p, pair<int,int> q) {
    return sqrt(dist2(p.first,p.second,q.first,q.second));
}

int main(void) {
    int i, j;
    pair<int,int> coo[1000];
    cin >> n;
    rep (i,n) cin >> coo[i].first >> coo[i].second;

    init();
    rep (i,n) REP (j,i+1,n-1) {
        if (dist2(coo[i].first,coo[i].second,coo[j].first,coo[j].second) <= 100)
            unite(i,j);
    }
    map<int,vector<int>> mp;
    rep (i,n) mp[find(i)].push_back(i);
    double ans = 1;
    for (auto& p : mp) {
        auto& v = p.second;
        rep (i,v.size()) rep (j,v.size())
            ans = max(ans,dist(coo[v[i]],coo[v[j]])+2);
    }
    cout << fixed << setprecision(7) << ans << endl;
    return 0;
}