import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int N = scanner.nextInt();
        int[] X = new int[N];
        int[] Y = new int[N];

        if (N == 0) {
            System.out.println(1);
            return;
        }

        for (int i = 0; i < N; i++) {
            X[i] = scanner.nextInt();
            Y[i] = scanner.nextInt();
        }
        UnionFind union = new UnionFind(N);
        for (int i = 0; i < N; i++) {
            for (int j = i + 1; j < N; j++) {
                if (Math.hypot(X[i] - X[j], Y[i] - Y[j]) <= 10) {
                    union.union(i, j);
                }
            }
        }
        double mx = 0;
        for (int i = 0; i < N; i++) {
            for (int j = i + 1; j < N; j++) {
                if (union.same(i, j)) {
                    double len = Math.hypot(X[i] - X[j], Y[i] - Y[j]);
                    if (mx < len) {
                        mx = len;
                    }
                }
            }
        }
        System.out.println(mx + 2);


    }


}

class UnionFind {
    int[] parent;
    int[] rank;

    public UnionFind(int N) {
        parent = new int[N];
        rank = new int[N];
        for (int i = 0; i < N; i++) {
            parent[i] = i;
        }
    }


    public int find(int A) {
        if (parent[A] == A) {
            return A;
        }
        return find(parent[A]);
    }

    public boolean same(int A, int B) {
        return find(A) == find(B);
    }


    public void union(int A, int B) {
        int Aroot = find(A);
        int Broot = find(B);

        if (rank[Aroot] > rank[Broot]) {
            parent[Broot] = Aroot;
        } else if (rank[Aroot] < rank[Broot]) {
            parent[Aroot] = Broot;
        } else if (Aroot != Broot) {
            parent[Aroot] = Broot;
            rank[Broot]++;
        }
    }

}