#include <iostream>
#include <sstream>
#include <vector>
using namespace std;

typedef struct HEAD {
    long x;
    long y;

} HEAD;





int main() {
    long N;

    cin >> N;

    int count = 0;

    HEAD heads[N];

    bool good = false;

    for (int i = 0; i < N; i++)
    {
        cin >> heads[i].x;
        cin >> heads[i].y;
    }

    HEAD stop[N];

    for (int i = 0; i < N; i++) {
        good = false;
        for (int j = 0; j < N; j++) {
            if (i != j && (stop[i].x != heads[i].x || stop[i].y != heads[i].y) && (heads[i].x == heads[j].x || heads[i].y == heads[j].y)) {
                good = true;
                stop[i].x = heads[i].x;
                stop[i].y = heads[i].y;
            }
        }

        if(!good) count++;
    }


    


    
    


        /*for (int i = 0; i < N; i++) {
        change = false;
        if (i > 0  && (heads[i].x != heads[i - 1].x && heads[i].y != heads[i - 1].y))
            {
                change = true;
            }
        if(change) count++;
        }*/
    cout << count << "\n";

    return 0;
}