#include <bits/stdc++.h>
using namespace std;
void File() {
  freopen("output.txt", "w", stdout);
  freopen("input.txt", "r", stdin);
}
void fast() {
  ios::sync_with_stdio(NULL);
  cout.tie(NULL);
  cin.tie(NULL);
}
const double pi = 2 * acos(0.0);
const int nn = 5e2 + 5;
const int oo = 0x3f3f3f3f;
int main() {
  fast();
  int n, ans = 0;
  pair<int, int> arr[nn];
  cin >> n;
  for (int i = 0; i < n; i++) cin >> arr[i].first >> arr[i].second;
  for (int i = 0; i < n; i++) {
    int cnt[4] = {};
    for (int j = 0; j < n; j++) {
      if (i == j) continue;
      if (arr[i].first > arr[j].first && arr[i].second == arr[j].second)
        cnt[0]++;
      else if (arr[i].first < arr[j].first && arr[i].second == arr[j].second)
        cnt[1]++;
      else if (arr[i].first == arr[j].first && arr[i].second > arr[j].second)
        cnt[2]++;
      else if (arr[i].first == arr[j].first && arr[i].second < arr[j].second)
        cnt[3]++;
      if (cnt[0] && cnt[1] && cnt[2] && cnt[3]) {
        ans++;
        break;
      }
    }
  }
  cout << ans << "\n";
  return 0;
}
