#include"bits/stdc++.h"

//#include<bits/stdc++.h>
using namespace std;
#define print(x) cout<<x<<endl;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a) for(int i=0;i<a;i++)
typedef long long ll;
typedef pair<int, int> PI;
typedef pair<int, PI> V;
const ll mod = 10000000000;
//union-find木実装
int par[100002];
int ran[100002];

//初期化
void init(int n) {
	rep(i, 0, n) {
		par[i] = i;
		ran[i] = 0;
	}
}

//木の根を求める
int find(int x) {
	if (par[x] == x) {
		return x;
	}
	else {
		return par[x] = find(par[x]);
	}
}

//ｘとｙの属する集合を併合
void unite(int x, int y) {
	x = find(x);
	y = find(y);
	if (x == y) return;

	if (ran[x] < ran[y]) {
		par[x] = y;
	}
	else {
		par[y] = x;
		if (ran[x] == ran[y])ran[x]++;
	}
}

//ｘとｙが同じ集合かどうか
bool same(int x, int y) {
	return find(x) == find(y);
}

int main() {
	int n;
	double x[1002], y[1002];
	double ans = 0;
	cin >> n;
	REP(i, n)cin >> x[i] >> y[i];
	init(n);
	REP(i, n)rep(j, i + 1, n) {
		if (pow(x[i] - x[j], 2.0) + pow(y[i] - y[j], 2.0) <= 100.0) {
			unite(i,j);
		}
	}
	REP(i, n)rep(j, i + 1, n) {
		if (same(i, j))ans = max(ans, sqrt(pow(x[i] - x[j], 2.0) + pow(y[i] - y[j], 2.0)) + 2.0);
	}
	printf("%10lf\n", ans);
	return 0;
}