#include <bits/stdc++.h>
using namespace std;
bool comp(int x, int y) { return x > y; }
int dx[] = {0, 0, 1, -1};
int dy[] = {1, -1, 0, 0};
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
int main() {
  int n;
  cin >> n;
  vector<pair<int, int> > a(n);
  for (int i = 0; i < n; i++) {
    int x, y;
    cin >> x >> y;
    a[i] = make_pair(x, y);
  }
  int res = 0;
  for (int i = 0; i < n; i++) {
    int x1 = a[i].first;
    int y1 = a[i].second;
    int upper = 0, lower = 0, right = 0, left = 0;
    for (int j = 0; j < n; j++) {
      if (i != j) {
        int x2 = a[j].first;
        int y2 = a[j].second;
        if (x2 > x1 && y1 == y2) right++;
        if (x2 < x1 && y1 == y2) left++;
        if (x1 == x2 && y2 > y1) upper++;
        if (x1 == x2 && y2 < y1) lower++;
      }
    }
    if (upper >= 1 && lower >= 1 && right >= 1 && left >= 1) res++;
  }
  cout << res << endl;
  return 0;
}
