#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
#define repr(i, a) for (int i = (a) - 1; i >= 0; i--)
#define repr2(i, a, b) for (int i = (b) - 1; i >= (a); i--)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

struct UF {
	vector<int> parent, size;
	UF(int n) : parent(n), size(n, 1) {
		rep (i, n) parent[i] = i;
	}
	int root(int x) {
		if (x == parent[x]) return x;
		else return parent[x] = root(parent[x]);
	}
	void unite(int x, int y) {
		x = root(x); y = root(y);
		if (x == y) return;
		if (size[x] > size[y]) swap(x, y);
		size[x] += size[y];
		parent[y] = x;
	}
	bool same(int x, int y) {
		return root(x) == root(y);
	}
};

typedef double D;
typedef complex<D> P;
const D eps = 1e-8;

D dot(P a, P b) {
	return real(conj(a) * b);
}

D cross(P a, P b) {
	return imag(conj(a) * b);
}

int N;
P ps[1000];

double G[1000][1000];

int main() {
	int N;
	cin >> N;
	rep (i, N) {
		double x, y;
		cin >> x >> y;
		ps[i] = P(x, y);
	}

	UF uf(N);

	rep (i, N) rep (j, N) {
		if (abs(ps[j] - ps[i]) <= 10) {
			uf.unite(i, j);	
		}
	}

	map<int, vector<int>> group;

	rep (i, N) {
		group[uf.root(i)].push_back(i);
	}

	double ans = 1;

	for (auto q : group) {
		vector<int> p = q.second;
		double dist = 0;
		rep (i, p.size()) {
			rep (j, p.size()) {
				dist = max(dist, abs(ps[p[j]] - ps[p[i]]));
			}
		}
		ans = max(ans, dist + 2);
	}

	printf("%.20f\n", ans);

	return 0;
}