#include <bits/stdc++.h>

using namespace std;

namespace {

    typedef double real;
    typedef long long ll;

    real EPS = 1e-8;

    template<class T> ostream& operator<<(ostream& os, const vector<T>& vs) {
        if (vs.empty()) return os << "[]";
        os << "[" << vs[0];
        for (int i = 1; i < vs.size(); i++) os << " " << vs[i];
        return os << "]";
    }
    template<class T> istream& operator>>(istream& is, vector<T>& vs) {
        for (auto it = vs.begin(); it != vs.end(); it++) is >> *it;
        return is;
    }

    struct Point {
        real x, y;
        Point() {}
        Point(real x, real y) : x(x), y(y) {}
        Point operator+(const Point& p) const { return Point(x + p.x, y + p.y); }
        Point operator-(const Point& p) const { return Point(x - p.x, y - p.y); }
        Point operator*(real k) const { return Point(k * x, k * y); }
        Point operator/(real k) const { return Point(x / k, y / k); }
    };
    real dot(const Point& a, const Point& b) { return a.x * b.x + a.y * b.y; }
    real cross(const Point& a, const Point& b) { return a.x * b.y - a.y * b.x; }
    real norm(const Point& a) { return sqrt(dot(a, a)); }
    Point rot90(const Point& p) { return Point(-p.y, p.x); } // 反時計回りに90度回転 
    real angle(const Point& a) { return atan2(a.y, a.x); } // x軸を反時計回りに何ラジアン回転させれば点aに乗るか
    ostream& operator<<(ostream& os, const Point& p) { return os << "(" << p.x << "," << p.y << ")"; }
    istream& operator>>(istream& is, Point& p) { return is >> p.x >> p.y; }

    struct UnionFind {
        int N;
        vector<int> P;
        UnionFind(int N) : N(N) {
            P.clear(); P.resize(N, -1);
        }
        int root(int x) {
            if (P[x] == -1) return x;
            return P[x] = root(P[x]);
        }
        int query(int x, int y) {
            return root(x) == root(y);
        }
        void merge(int x, int y) {
            x = root(x); y = root(y);
            if (x == y) return;
            P[x] = y;
        }
    };

    int N;
    vector<Point> P;
    void input() {
        cin >> N;
        P.resize(N);
        cin >> P;
    }

    void solve() {
        real ans = 0;
        UnionFind uf(N);
        for (int i = 0; i < N; i++) {
            for (int j = i + 1; j < N; j++) {
                const Point& a = P[i];
                const Point& b = P[j];
                if ( norm(a - b) < 10.0 + EPS ) {
                    uf.merge(i, j);
                }
            }
        }
        for (int i = 0; i < N; i++) {
            for (int j = i + 1; j < N; j++) {
                const Point& a = P[i];
                const Point& b = P[j];
                if (uf.query(i, j)) {
                    ans = max(ans, norm(a - b));
                }
            }
        }
        if (N == 0) {
            cout << setprecision(12) << 1 << endl;
        } else {
            cout << setprecision(12) << ans + 2 << endl;
        }
    }
}

int main() {
    input(); solve();
    return 0;
}