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

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)]);
    }
};

int main() {
    int N, X[1010], Y[1010];
    cin >> N;
    for (int i = 0; i < N; i++) {
        cin >> X[i] >> Y[i];
    }

    auto check = [&](int a, int b) {
        return abs(X[a] - X[b]) * abs(X[a] - X[b]) + abs(Y[a] - Y[b]) * abs(Y[a] - Y[b]) <= 100;
    };

    UnionFind uf(N);
    for (int i = 0; i < N; i++) {
        for (int j = i + 1; j < N; j++) {
            if (check(i, j))
                uf.unite(i, j);
        }
    }

    double ans = 1;
    auto dist = [&](int a, int b) {
        return sqrt(abs(X[a] - X[b]) * abs(X[a] - X[b]) + abs(Y[a] - Y[b]) * abs(Y[a] - Y[b])) + 2;
    };

    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            if (uf.same(i, j)) {
                ans = max(ans, dist(i, j));
            }
        }
    }
    cout << fixed << setprecision(7) << ans << endl;
}