#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>
#include <cmath>

using namespace std;

class UnionFind {
public:
	vector<int> parent;
	int trees;

	UnionFind(int n) {
		trees = n;
		parent.assign(n, 0);
		for (int i = 0; i < n; i++) {
			parent[i] = i;
		}
	}

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

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

	void unite(int x, int y) {
		x = find(x);
		y = find(y);

		if (x != y) {
			parent[x] = y;
			trees--;
		}
	}

	int count() {
		return trees;
	}
};

int main() {
	int n;

	cin >> n;
	if (n == 0) {
		cout << 1 << endl;
		return 0;
	}

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

	vector< vector<double> > len(n, vector<double>(n, 0));

	for (int i = 0; i < n; i++) {
		for (int j = i + 1; j < n; j++) {
			len[i][j] = sqrt(pow(x[i] - x[j], 2) + pow(y[i] - y[j], 2));
			len[j][i] = len[i][j];
		}
	}


	UnionFind uf(n);
	for (int i = 0; i < n; i++) {
		for (int j = i + 1; j < n; j++) {
			if (len[i][j] <= 10.0) {
				uf.unite(i, j);
			}
		}
	}

	double max_len = 0;
	for (int i = 0; i < n; i++) {
		for (int j = i + 1; j < n; j++) {
			if (uf.same(i, j)) {
				max_len= max(max_len, len[i][j]);
			}
		}
	}

	max_len += 2;
	printf("%.9lf\n", max_len);
	return 0;
}