#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(ri,n) for(int ri = (int)(n-1); ri >= 0; ri--)
#define rep2(i,x,n) for(int i = (int)(x); i < (int)(n); i++)
#define rrep2(ri,x,n) for(int ri = (int)(n-1); ri >= (int)(x); ri--)
#define repit(itr,x) for(auto itr = x.begin(); itr != x.end(); itr++)
#define rrepit(ritr,x) for(auto ritr = x.rbegin(); ritr != x.rend(); ritr++)
#define ALL(x) x.begin(), x.end()
using ll = long long;
using namespace std;

int main(){
  int n;
  cin >> n;
  pair<int, int> ms;
  int a, b;
  cin >> a >> b;
  ms = {a, b};
  vector<pair<int, int>> ab(n-1);
  rep(i, n-1){
    int a, b;
    cin >> a >> b;
    ab.at(i) = {a, b};
  }
  int ans = 0;
  vector<vector<double>> vd(n-1, vector<double>(n-1));
  vector<bool> chk(n-1, false);
  vector<double> dv(n-1);
  set<pair<int, pair<int, int>>> se;
  rep(i, n-1){
    auto [a, b] = ab.at(i);
    double d = hypot(ms.first - a, ms.second - b);
    dv.at(i) = d;
    rep2(j, i+1, n-1){
      auto [a2, b2] = ab.at(j);
      double dis = hypot(a - a2, b - b2);
      se.insert({dis, {i, j}});
    }
  }
  for(auto pp : se){
    auto [dis, ij] = pp;
    auto [i, j] = ij;
    if(chk.at(i) == true || chk.at(j) == true) continue;
    if(dv.at(i) < dis || dv.at(j) < dis) continue;
    chk.at(i) = true;
    chk.at(j) = true;
  }
  rep(i, n-1){
    if(chk.at(i) == false) ans++;
  }
  cout << ans << endl;
  return 0;
}