#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

class UnionFind{
public:
    UnionFind(int _n):n(_n), cnt(_n), par(_n), rank(_n), size(_n, 1){
        for(int i=0;i<n;++i) par[i]=i;
    }
    int find(int k){
        return (k==par[k])?k:(par[k]=find(par[k]));
    }
    int operator[](int k){
        return find(k);
    }
    int getSize(int k){
        return size[find(k)];
    }
    void unite(int x, int y){
        x = find(x); y = find(y);
        if(x==y) return;
        --cnt;
        if(rank[x] < rank[y]){
            par[x] = y;
            size[y] += size[x];
        }else{
            par[y] = x;
            size[x] += size[y];
            if(rank[y] == rank[x]) ++rank[x];
        }
    }
    int count(){
        return cnt;
    }
private:
    int n, cnt;
    vector<int> par, rank, size;
};

int sq(int x, int y){
    return x*x + y*y;
}

int b[2021][2021];
vi a[1000];

int main(){
    int N, R = 1010;
    double ans = 1;
    cin >> N;
    vi X(N), Y(N);
    MEM(b, -1);
    rep(i, N){
        cin >> X[i] >> Y[i];
        X[i] += R;
        Y[i] += R;
        b[X[i]][Y[i]] = i;
    }
    UnionFind uf(N);
    rep(i, N){
        FOR(x, X[i] - 10, X[i] + 11)FOR(y, Y[i] - 10, Y[i] + 11)if(sq(x - X[i], y - Y[i]) <= 100 && b[x][y]!=-1){
            uf.unite(i, b[x][y]);
        }
    }
    rep(i, N)a[uf[i]].push_back(i);
    rep(i, N)if(sz(a[i])){
        double ma = 0;
        rep(j, sz(a[i]))rep(k, j)smax(ma, hypot(X[a[i][j]] - X[a[i][k]], Y[a[i][j]] - Y[a[i][k]]));
        smax(ans, ma + 2);
    }
    printf("%0.20f\n", ans);
}