#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)




template<int um> class UF {
public:
	vector<int> par;
	UF() { par = vector<int>(um, 0); rep(i, 0, um) par[i] = i; }
	int operator[](int x) { return par[x] == x ? x : par[x] = operator[](par[x]); }
	void operator()(int x, int y)
	{
		x = operator[](x); y = operator[](y);
		if (x != y) par[x] = y;
	}
};
//-----------------------------------------------------------------
int N;
int X[1010], Y[1010];
//-----------------------------------------------------------------
int main()
{
	cin >> N;
	rep(i, 0, N) scanf("%d %d", &X[i], &Y[i]);

	if (N == 0) {
		printf("1\n");
		return 0;
	}

	UF<1010> uf;
	rep(i, 0, N) rep(j, i + 1, N) {
		int dd = (X[i] - X[j]) * (X[i] - X[j]) + (Y[i] - Y[j]) * (Y[i] - Y[j]);
		if (dd <= 100) {
			uf(i, j);
		}
	}

	double ans = 0;
	rep(i, 0, N) rep(j, 0, N) if (uf[i] == uf[j]) {
		int dd = (X[i] - X[j]) * (X[i] - X[j]) + (Y[i] - Y[j]) * (Y[i] - Y[j]);
		double d = sqrt(dd);
		ans = max(ans, d + 2.0f);
	}
	printf("%.10f\n", ans);
}