#include <iostream>
#include <cmath>
#include <iomanip>
using namespace std;

const int MAX_N = 1010;

int x[MAX_N], y[MAX_N];
bool connected[MAX_N][MAX_N];

int square_dist(int x1, int y1, int x2, int y2) {
    return (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
}

int main() {
    int n;
    cin >> n;

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

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            int d = square_dist(x[i], y[i], x[j], y[j]);
            if (d <= 10 * 10) connected[i][j] = true;
        }
    }

    for (int k = 0; k < n; k++) {
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                connected[i][j] |= connected[i][k] && connected[k][j];
            }
        }
    }
    double ans = 1.0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (connected[i][j]) {
                double dist = sqrt(square_dist(x[i], y[i], x[j], y[j]));
                ans = max(ans, dist + 2.0);
            }
        }
    }
    cout << fixed << setprecision(10) << ans << endl;

    return 0;
}