#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;
using mint = modint998244353;

int main() {
  int N; cin >> N;
  vector<ll> x(N), y(N);
  for (int i = 0; i < N; i++) cin >> x[i] >> y[i];
  vector<tuple<ll, int, int>> v;
  for (int i = 0; i < N; i++) {
    for (int j = i + 1; j < N; j++) {
      ll d = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
      v.push_back({d, i, j});
    }
  }
  sort(v.begin(), v.end());
  int cnt = 0;
  vector<bool> used(N, false);
  for (auto [d, i, j]: v) {
    if (used[i] or used[j]) continue;
    if (i == 0) {
      used[j] = true, cnt++;
    } else if (j == 0) {
      used[i] = true, cnt++;
    } else {
      used[i] = used[j] = true;
    }
  }
  cout << cnt << endl;
  return 0;
}