#define rep(i,n) for (int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

const int INF=1e9+7;

int main(){
  int n;
  cin>>n;
  
  vector<ll> X(n),Y(n);
  rep(i,n) cin>>X[i]>>Y[i];
  
  if(n==1){
    cout<<0<<endl;
    return 0;
  }
  if(n==2){
    cout<<1<<endl;
    return 0;
  }
  
  vector<vector<ll>> A(n,vector<ll>(n));
  vector<ll> B;
  for(int i=0;i<n;i++){
    for(int j=i+1;j<n;j++){
      A[i][j]=(X[i]-X[j])*(X[i]-X[j])+(Y[i]-Y[j])*(Y[i]-Y[j]);
      B.push_back(A[i][j]);
    }
  }
  sort(ALL(B));
  B.erase(unique(ALL(B)),B.end());
  set<tuple<int,int,int>> s;
  for(int i=0;i<n;i++){
    for(int j=i+1;j<n;j++){
      A[i][j]=lower_bound(ALL(B),A[i][j])-B.begin();
      s.insert({A[i][j],i,j});
    }
  }
  vector<int> D(1010,1);
  int rem=n;
  int cnt=0;
  for(auto x:s){
    if(rem==1) break;
    else if(rem==2){
      cnt++;
      break;
    }
    int a=get<1>(x);
    int b=get<2>(x);
    int c=get<0>(x);
    if(D[a]==0 || D[b]==0) continue;
    else if(a==0 && D[b]==1){
      D[b]=0;
      rem--;
      cnt++;
      continue;
    }
    else{
      D[a]=0,D[b]=0;
      rem-=2;
    }
  }
  cout<<cnt<<endl;

  return 0;
}