#include <bits/stdc++.h>
using namespace std;
using ll = long long int;

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(begin(v), end(v));
  vector<bool> used(n, false);
  int cnt = 0;
  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 << "\n";
}