#include <iostream>
#include <iomanip>
#include <cmath>
#include <numeric>
#include <vector>

struct UnionFind {
    std::vector<int> par, sz;
    int gnum;

    explicit UnionFind(int n)
        : par(n), sz(n, 1), gnum(n) {
        std::iota(par.begin(), par.end(), 0);
    }

    int find(int v) {
        return (par[v] == v) ? v : (par[v] = find(par[v]));
    }

    void unite(int u, int v) {
        u = find(u), v = find(v);
        if (u == v) return;

        if (sz[u] < sz[v]) std::swap(u, v);
        sz[u] += sz[v];
        par[v] = u;
        --gnum;
    }

    bool same(int u, int v) { return find(u) == find(v); }
    bool ispar(int v) { return v == find(v); }
    int size(int v) { return sz[find(v)]; }
};

using ldouble = long double;

void solve() {
    int n;
    std::cin >> n;

    std::vector<int> xs(n), ys(n);
    for (int i = 0; i < n; ++i) std::cin >> xs[i] >> ys[i];

    UnionFind uf(n);
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < i; ++j) {
            int dx = xs[i] - xs[j],
                dy = ys[i] - ys[j];

            if (dx * dx + dy * dy <= 10 * 10) {
                uf.unite(i, j);
            }
        }
    }

    ldouble ans = 1;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j <= i; ++j) {
            if (!uf.same(i, j)) continue;
            ldouble dx = xs[i] - xs[j],
                    dy = ys[i] - ys[j];
            ans = std::max(ans, std::hypot(dx, dy) + 2);
        }
    }

    std::cout << ans << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed << std::setprecision(10);

    solve();

    return 0;
}