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

struct UnionFind{
    vector<int> parent;
    UnionFind(int n): parent(vector<int>(n, -1)){}
    
    int root(int x){
        if(parent[x] < 0) return x;
        else return parent[x] = root(parent[x]);
    }

    int count(int x){
        return -parent[root(x)];
    }

    bool same(int x, int y){
        return root(x) == root(y);
    }

    void unite(int x, int y){
        if(same(x, y)) return;
        x = root(x);
        y = root(y);
        if(count(x) < count(y)) swap(x, y);
        parent[x] += parent[y];
        parent[y] = x;
    }
};

int main(){
    int n; cin >> n;
    vector<int> x(n), y(n);
    for(int i = 0; i < n; i++) cin >> x[i] >> y[i];

    auto dist2 = [&](int i, int j){
        return abs(x[i]-x[j])*abs(x[i]-x[j]) + abs(y[i]-y[j])*abs(y[i]-y[j]);
    };

    UnionFind uf(n);
    for(int i = 0; i < n; i++){
        for(int j = 0; j < n; j++){
            if(dist2(i, j) <= 10*10) uf.unite(i, j);
        }
    }

    double ans = 1.0;
    for(int i = 0; i < n; i++){
        for(int j = 0; j < n; j++){
            if(uf.same(i, j)){
                ans = max(ans, sqrt(dist2(i, j))+2.0);
            }
        }
    }
    cout << fixed << setprecision(10) << ans << endl;
    return 0;
}