#include <bits/stdc++.h>
using namespace std;
bool binary(vector<int> v, int key) {
  int lo = 0, hi = v.size() - 1;
  while (lo <= hi) {
    int mid = (lo + hi) / 2;
    if (v[mid] == key)
      return true;
    else if (v[mid] < key)
      lo = mid + 1;
    else
      hi = mid - 1;
  }
  return false;
}
int main() {
  int n, ans = 0, l = 0, r = 0, u = 0, d = 0;
  cin >> n;
  vector<pair<int, int>> v;
  for (int i = 0; i < n; i++) {
    int t1, t2;
    cin >> t1 >> t2;
    v.push_back(make_pair(t1, t2));
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (v[j].first == v[i].first && v[j].second < v[i].second) d++;
      if (v[j].first == v[i].first && v[j].second > v[i].second) u++;
      if (v[j].first < v[i].first && v[j].second == v[i].second) l++;
      if (v[j].first > v[i].first && v[j].second == v[i].second) r++;
    }
    if (d && r && l && u) ans++;
    d = 0, r = 0, l = 0, u = 0;
  }
  cout << ans;
  return 0;
}
