#include <algorithm>
#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
template<class T> T dist2(T x, T y) { return x * x + y * y; }

struct UnionFind {
    vector<int> data;
    int sz;
    UnionFind(int sz) : data(sz, -1), sz(sz) { }
    bool unionSet(int x, int y) {
        if ((x = root(x)) == (y = root(y))) return false;
        if (data[x] > data[y]) swap(x, y);
        data[x] += data[y]; data[y] = x; sz--;
        return true;
    }
    bool findSet(int x, int y) { return root(x) == root(y); }
    int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
    int size(int x) { return -data[root(x)]; }
    int size() { return sz; }
};

#include <iomanip>
int main() {
    cout << fixed << setprecision(12);
    int n; cin >> n;
    vector<int> x(n), y(n);
    for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
    UnionFind uf(n);
    for (int i = 0; i < n; i++) for (int j = i + 1; j < n; j++) {
        if (dist2(x[i] - x[j], y[i] - y[j]) <= 100) uf.unionSet(i, j);
    }
    double ans = (n == 0 ? 1.0 : 2.0);
    for (int i = 0; i < n; i++) for (int j = i + 1; j < n; j++) {
        if (uf.findSet(i, j)) {
            double d = sqrt(dist2(x[i] - x[j], y[i] - y[j])) + 2;
            ans = max(ans, d);
        }
    }
    cout << ans << endl;
    return 0;
}