#include <bits/stdc++.h>
using namespace std;


vector<pair<int, int>> convex_hull(vector<pair<int, int>> V) {
    auto cross = [](pair<int, int> a, pair<int, int> b, pair<int, int> c) {
        b.first -= a.first;
        c.first -= a.first;
        b.second -= a.second;
        c.second -= a.second;
        return (long long)b.first * c.second - (long long)b.second * c.first;
    };
    int n = (int)V.size();
    sort(V.begin(), V.end(), [](pair<int, int> a, pair<int, int> b) {
        return a.first != b.first ? a.first < b.first : a.second < b.second;
    });
    if (n == 1) return V;
    int k = 0;
    vector<pair<int, int>> ret(n * 2);
    for (int i = 0; i < n; i++) {
        while (k > 1 && cross(ret[k - 1], V[i], ret[k - 2]) >= 0)
            k--;
        ret[k++] = V[i];
    }
    for (int i = n - 2, t = k; i >= 0; i--) {
        while (k > t && cross(ret[k - 1], V[i], ret[k - 2]) >= 0)
            k--;
        ret[k++] = V[i];
    }
    ret.resize(k - 1);
    return ret;
}


struct UnionFind {
    vector<int> data;
    UnionFind(int n) {
        data.assign(n, -1);
    }
    bool unite(int x, int y) {
        x = root(x), y = root(y);
        if (x == y)
            return (false);
        if (data[x] > data[y])
            swap(x, y);
        data[x] += data[y];
        data[y] = x;
        return (true);
    }
    int root(int k) {
        if (data[k] < 0)
            return (k);
        return (data[k] = root(data[k]));
    }
    bool same(int x, int y) {
        return root(x) == root(y);
    }
    int size(int k) {
        return (-data[root(k)]);
    }
};

vector<int> B[2010][2010];
int main() {
    int N;
    vector<pair<int, int>> V;
    cin >> N;
    for (int i = 0; i < N; i++) {
        int x, y;
        cin >> x >> y;
        V.push_back({x + 10000, y + 10000});
    }
    if (N == 0) {
        cout << 1 << endl;
        return 0;
    }

    UnionFind uf(N);
    auto check = [&](int a, int b) {
        int xa = V[a].first, ya = V[a].second, xb = V[b].first, yb = V[b].second;
        return abs(xa - xb) * abs(xa - xb) + abs(ya - yb) * abs(ya - yb) <= 100;
    };


    for (int i = 0; i < N; i++) {
        int& x = V[i].first;
        int& y = V[i].second;
        int X = x / 10 + 1;
        int Y = y / 10 + 1;
        for (int dx = -1; dx <= 1; dx++) {
            for (int dy = -1; dy <= 1; dy++) {
                for (auto& n : B[X + dx][Y + dy]) {
                    if (check(i, n))
                        uf.unite(i, n);
                }
            }
        }
        B[X][Y].push_back(i);
    }

    map<int, vector<int>> V2;
    for (int i = 0; i < N; i++) {
        if (!V2.count(uf.root(i))) {
            V2[uf.root(i)].reserve(uf.size(i));
        }
        V2[uf.root(i)].push_back(i);
    }

    auto dist = [](const pair<int, int>& a, const pair<int, int>& b) {
        return sqrt(abs(a.first - b.first) * abs(a.first - b.first) + abs(a.second - b.second) * abs(a.second - b.second));
    };

    double ans = 0;
    for (auto& p : V2) {
        vector<pair<int, int>> V3;
        V3.reserve(p.second.size());
        for (auto& a : p.second)
            V3.push_back({V[a].first, V[a].second});
        V3 = convex_hull(V3);
        for (auto& a : V3)
            for (auto& b : V3)
                ans = max(ans, dist(a, b) + 2);
    }

    cout << fixed << setprecision(9) << ans << endl;
}