#include <bits/stdc++.h>
#include <atcoder/dsu>

using namespace std;
using namespace atcoder;

int main() {
    int N;
    cin >> N;
    map<pair<int,int>, vector<tuple<int,int,int>>> XY;
    vector<int> X, Y;
    for (int n = 0; n < N; ++n) {
        int x, y;
        cin >> x >> y;
        XY[{x / 10, y / 10}].push_back({x, y, n});
        X.push_back(x);
        Y.push_back(y);
    }
    dsu UF(N);
    for (auto& [ij, lst] : XY) {
        int i=ij.first;
        int j=ij.second;
        for (int di = -1; di <= 1; ++di) {
            for (int dj = -1; dj <= 1; ++dj) {
                if (!XY.count({i + di, j + dj})) {
                    continue;
                }
                for (auto& [x, y, n] : XY[{}]) {
                    for (auto& [xx, yy, nn] : XY[{i + di, j + dj}]) {
                        if ((x - xx) * (x - xx) + (y - yy) * (y - yy) <= 100) {
                            UF.merge(n, nn);
                        }
                    }
                }
            }
        }
    }
    long double ans = 1;
    for (auto& lst : UF.groups()) {
        for (int i : lst) {
            for (int j : lst) {
                ans = max(ans, sqrt((long double)(X[i] - X[j]) * (X[i] - X[j]) + (Y[i] - Y[j]) * (Y[i] - Y[j])) + 2);
            }
        }
    }
    cout << fixed << setprecision(10);
    cout << ans << endl;
    return 0;
}