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

using namespace std;
//using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define MOD 1000000007

ll pp(ll k){return k*k;}
ll d2(pair<ll,ll> a,pair<ll,ll> b){
  return pp(a.first-b.first)+pp(a.second-b.second);
}
struct info{
  ll dist,a,b;
  bool operator<(const info& o)const{return dist < o.dist;}
  bool operator>(const info& o)const{return dist > o.dist;}
};

int main(){
  
  int n;
  cin >> n;
  vector<pair<ll,ll>> v(n);
  rep(i,n)cin >> v[i].first >> v[i].second;
  priority_queue<info,vector<info>,greater<info>> que;
  rep(i,n)for(int j = i+1;j < n;j++){
    que.push(info{d2(v[i],v[j]),i,j});
  }
  set<int> era;
  int res = 0;
  while(!que.empty()){
    info k = que.top();que.pop();
    if(era.count(k.a) || era.count(k.b))continue;
    if(k.dist < d2(v[0],v[k.a]) && k.dist < d2(v[0],v[k.b])){
      era.insert(k.a);
      era.insert(k.b);
    }else if(k.dist >= d2(v[0],v[k.a])){
      era.insert(k.a);
      res++;
    }else if(k.dist >= d2(v[0],v[k.b])){
      era.insert(k.b);
      res++;
    }else{
      era.insert(k.a);
      era.insert(k.b);
      res += 2;
    }
  }
  cout << res << "\n";


  return 0;
}