#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, j;
  cin >> n;
  vector<pair<int, int>> v;
  for (i = 0; i < n; i++) {
    int x, y;
    cin >> x >> y;
    v.push_back(make_pair(x, y));
  }
  int ans = 0;
  int total = 0;
  bool u, d, l, r;
  for (i = 0; i < n; i++) {
    for (j = 0; j < n; j++) {
      if (v[i].first > v[j].first && v[i].second == v[j].second) d = true;
      if (v[i].first < v[j].first && v[i].second == v[j].second) u = true;
      if (v[i].second > v[j].second && v[i].first == v[j].first) l = true;
      if (v[i].second < v[j].second && v[i].first == v[j].first) r = true;
    }
    if (d && u && l && r) total++;
    d = false;
    u = false;
    l = false;
    r = false;
  }
  cout << total;
}
