#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
using ll = long long;

#include<iomanip>
#include<math.h>

ll cross(ll a,ll b,ll c,ll d){
    return a * d - b * c;
}

int ccw(pair<ll,ll> a,pair<ll,ll> b,pair<ll,ll> c) {
    ll dx = b.first - a.first;
    ll dy = b.second - a.second;
    ll ddx = c.first - b.first;
    ll ddy = c.second - b.second;
    ll now = cross(dx,dy,ddx,ddy);
    if(now<0) return -1;
    if(now>0) return 1;
    return 0;
}

long double calc(vector<pair<ll,ll>> use) {
    int n = use.size();
    sort(use.begin(),use.end());
    if(n==1) return 2;

    vector<pair<ll,ll>> upper,lower;
    for(int i = 0;i<n;i++){
        while(upper.size()>=2){
            int m = upper.size();
            if(ccw(upper[m-2],upper[m-1],use[i])!=-1) upper.pop_back();
            else break;
        }
        upper.push_back(use[i]);
    }
    for(int i = 0;i<n;i++){
        while(lower.size()>=2){
            int m = lower.size();
            if(ccw(lower[m-2],lower[m-1],use[i])!=1) lower.pop_back();
            else break;
        }
        lower.push_back(use[i]);
    }

    long double ans = 0;
    reverse(lower.begin(),lower.end());
    for(int i = 1;i+1<lower.size();i++) upper.push_back(lower[i]);

    int ni = 0;
    int m = upper.size();
    auto d = [&](int i,int j) -> long double {
        ll dx = upper[i].first - upper[j].first;
        ll dy = upper[i].second - upper[j].second;
        return sqrt(dx*dx+dy*dy);
    };

    for(int i = 0;i<m;i++){
        while(true){
            ans = max(ans,d(i,ni));
            int nj = ni + 1;
            if(nj==m) nj = 0;
            if(nj==i) break;
            if(d(i,nj)>d(i,ni)) ni = nj;
            else break;
        }
        ans = max(d(i,ni),ans);
    }

    return ans + 2;
}

#include<atcoder/dsu>
#include<map>
int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int n;
    cin>>n;
    vector<ll> x(n),y(n);
    for(int i = 0;i<n;i++) cin>>x[i]>>y[i];
    atcoder::dsu uf(n);
    map<pair<ll,ll>,int> memo;
    for(int i = 0;i<n;i++) memo[make_pair(x[i],y[i])] = i;
    long double ans = 1;
    for(int i = 0;i<n;i++){
        for(int ni = -10;ni<=10;ni++){
            for(int nj = -10;nj<=10;nj++){
                ll now = ni * ni + nj * nj;
                if(now>100) continue;
                pair<ll,ll> want = make_pair(x[i]+ni,y[i]+nj);
                if(memo.find(want)!=memo.end()) {
                    uf.merge(i,memo[want]);
                }
            }
        }
    }

    for(auto&now:uf.groups()){
        vector<pair<ll,ll>> use;
        for(int i:now) use.push_back(make_pair(x[i],y[i]));
        ans = max(ans,calc(use));
    }

    cout<<setprecision(30)<<fixed<<ans<<endl;

}