#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-9;

struct union_find {
	vector<int> v;
	union_find(int n) : v(n, -1) {}
	int find(int x) { return (v[x] < 0) ? x : (v[x] = find(v[x])); }
	void unite(int x, int y) {
		x = find(x); y = find(y);
		if (x != y) {
			if (-v[x] < -v[y]) swap(x, y);
			v[x] += v[y]; v[y] = x;
		}
	}
	bool same(int x, int y) { return find(x) == find(y); }
	int size(int x) { return -v[find(x)]; }
};

int main() {
	int N; cin >> N;
	if (N == 0) {
		cout << 1 << endl;
		return 0;
	}
	vector<int> X(N), Y(N);
	for (int i = 0; i < N; i++)
		cin >> X[i] >> Y[i];
	union_find uf(N);
	for (int i = 0; i < N; i++)
		for (int j = 0; j < N; j++) {
			int dx = X[i] - X[j], dy = Y[i] - Y[j];
			if (dx * dx + dy * dy <= 10 * 10)
				uf.unite(i, j);
		}
	double maxi = 0;
	for (int i = 0; i < N; i++)
		for (int j = 0; j < N; j++)
			if (uf.same(i, j)) {
				int dx = X[i] - X[j], dy = Y[i] - Y[j];
				maxi = max(maxi, sqrt((double)dx * dx + dy * dy));
			}
	printf("%.10f\n", maxi + 2);
}