#include <bits/stdc++.h>
using namespace std;

int main() {

    int n;
    scanf("%d", &n);

    unordered_map<int, int> xs;
    unordered_map<int, int> ys; 
    vector<pair<int, int>> pts(n);

    for (int i = 0; i < n; i++) {
        int a,b;
        scanf("%d %d", &a, &b);
        pts[i] = {a, b};
        xs[a]++;
        ys[b]++;
    }

    int cnt = 0;

    for (int i = 0; i < n; i++) {
        if (xs[pts[i].first] <= 1 && ys[pts[i].second] <= 1) {
            cnt++;
        }
    }

    printf("%d\n", cnt);


    return 0;
}