V

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

int INF = 1001;
vector<vector<int>> arr(INF, vector<int>(INF));
vector<int> color(INF, 0);
int n;

void f(int i) {
    color[i] = 1;
    for (int j = 1; j <= n; j++) {
        if (color[j] == 0 && ((arr[0][i] == arr[0][j]) || (arr[1][i] == arr[1][j]))) {
            f(j);
        }
    }
}

int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> arr[0][i] >> arr[1][i];
    }

    int ans = -1;
    for (int i = 1; i <= n; i++) {
        if (color[i] == 0) {
            f(i);
            ans++;
        }
    }
    cout << ans;
    return 0;
}