#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
#include <numeric>
#include <cmath>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <complex>
#include <string.h>
#include <unordered_set>
#include <unordered_map>
#include <bitset>
#include <iomanip>
#include <sys/time.h>
#include <random>
using namespace std;

#define endl '\n'
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define UNIQ(v) (v).erase(unique((v).begin(), (v).end()), (v).end())

typedef long long ll;
typedef long double ld;
typedef pair<int, int> P;
typedef complex<double> comp;
typedef vector< vector<ld> > matrix;
struct pairhash {
public:
    template<typename T, typename U>
    size_t operator()(const pair<T, U> &x) const {
	size_t seed = hash<T>()(x.first);
	return hash<U>()(x.second) + 0x9e3779b9 + (seed<<6) + (seed>>2);
    }
};
const int inf = 1e9 + 9;
const ll mod = 1e9 + 7;
const double eps = 1e-8;
const double pi = acos(-1);

int n;
double x[1010], y[1010];

class UnionFind {
private:
    static const int MAX = 1010;
    int par[MAX];
    int r[MAX];
public:
    UnionFind(int n = MAX) {
	for (int i = 0; i < n; i++) {
	    par[i] = i;
	    r[i] = 0;
	}
    }

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

    void unite(int x, int y) {
	x = find(x);
	y = find(y);
	if (x == y) return;
	if (r[x] < r[y]) {
	    par[x] = y;
	} else {
	    par[y] = x;
	    if (r[x] == r[y]) r[x]++;
	}
    }

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

double dist(int i, int j) {
    return sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
}

double solve() {
    if (n == 0) return 1.0;
    UnionFind uf(n);
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < i; j++) {
            if (dist(i, j) < 10 + eps)
                uf.unite(i, j);
        }
    }

    double res = 0.0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < i; j++) {
            if (uf.same(i, j))
                res = max(res, dist(i, j));
        }
    }
    return res + 2.0;
}

void input() {
    cin >> n;
    for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);

    input();
    cout << solve() << endl;
}