#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n - 1); i >= 0; i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
using namespace std;
using ll = long long;
const int INF = 1e9;
const ll LINF = 1e18;
template <class T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
    if (b < a) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
vector<T> make_vec(size_t a) {
    return vector<T>(a);
}
template <class T, class... Ts>
auto make_vec(size_t a, Ts... ts) {
    return vector<decltype(make_vec<T>(ts...))>(a, make_vec<T>(ts...));
}
template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
    for (int i = 0; i < int(v.size()); i++) {
        is >> v[i];
    }
    return is;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    for (int i = 0; i < int(v.size()); i++) {
        os << v[i];
        if (i < int(v.size()) - 1) os << ' ';
    }
    return os;
}
#pragma region UnionFind
#include <vector>
struct UnionFind {
    int n;
    std::vector<int> data;
    UnionFind(int _n) : n(_n), data(_n, -1) {
    }
    int root(int x) {
        return (data[x] < 0) ? x : data[x] = root(data[x]);
    }
    bool unite(int x, int y) {
        x = root(x);
        y = root(y);
        if (x != y) {
            if (data[y] < data[x]) std::swap(x, y);
            data[x] += data[y];
            data[y] = x;
        }
        return x != y;
    }
    bool find(int x, int y) {
        return root(x) == root(y);
    }
    int size(int x) {
        return -data[root(x)];
    }
    std::vector<std::vector<int>> groups() {
        std::vector<int> root_buf(n), group_size(n);
        for (int i = 0; i < n; i++) {
            root_buf[i] = root(i);
            group_size[root_buf[i]]++;
        }
        std::vector<std::vector<int>> ret(n);
        for (int i = 0; i < n; i++) {
            ret[i].reserve(group_size[i]);
        }
        for (int i = 0; i < n; i++) {
            ret[root_buf[i]].push_back(i);
        }
        ret.erase(std::remove_if(
                      ret.begin(), ret.end(),
                      [&](const std::vector<int>& v) { return v.empty(); }),
                  ret.end());
        return ret;
    }
};
#pragma endregion
int main() {
    int n;
    cin >> n;
    if (n == 0) {
        cout << 1 << '\n';
        return 0;
    }
    vector<int> x(n), y(n);
    rep(i, n) cin >> x[i] >> y[i];
    UnionFind uf(n);
    rep(i, n) rep(j, i) {
        if ((x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]) <=
            100) {
            uf.unite(i, j);
        }
    }
    double ans = 2;
    rep(i, n) rep(j, i) if (uf.find(i, j)) {
        chmax(ans, hypot(x[i] - x[j], y[i] - y[j]) + 2.0);
    }
    cout << fixed << setprecision(20);
    cout << ans << '\n';
}