#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  vector<int> x(N), y(N);
  for (int i = 0; i < N; i++){
    cin >> x[i] >> y[i];
  }
  vector<tuple<double, int, int>> t;
  for (int i = 0; i < N; i++){
    for (int j = i + 1; j < N; j++){
      double d = hypot(x[j] - x[i], y[j] - y[i]);
      t.push_back(make_tuple(d, i, j));
    }
  }
  sort(t.begin(), t.end());
  int cnt = t.size();
  vector<bool> r(N, true);
  int ans = 0;
  for (int i = 0; i < cnt; i++){
    int x = get<1>(t[i]);
    int y = get<2>(t[i]);
    if (r[x] && r[y]){
      if (x == 0){
        ans++;
        r[y] = false;
      } else {
        r[x] = false;
        r[y] = false;
      }
    }
  }
  cout << ans << endl;
}