#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n); i++)
typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;
typedef tuple<ll,int,int> TP;

int main() {
  int n;
  cin >> n;
  vector<ll> x(n), y(n);
  rep(i,n) cin >> x[i] >> y[i];
  vector<TP> v;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (i == j) continue;
      ll d = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
      v.emplace_back(make_tuple(d, i, j));
    }
  }
  vector<int> used(n, 0);
  sort(v.begin(), v.end());
  int res = 0;
  for (auto e : v) {
    ll d;
    int a, b;
    tie(d, a, b) = e;
    if (used[a]) continue;
    if (used[b]) continue;
    if (a == 0 || b == 0) res++;
    if (a != 0) used[a] = 1;
    if (b != 0) used[b] = 1;
  }
  cout << res << endl;
  return 0;
}