#include <iostream>
#include <vector>
#include <cassert>
#include <map>
#include <set>
using namespace std;

class UnionSet {
public:
    #define DP_SIZE 400001
    int dp[DP_SIZE];
    void unite(int x, int y) {
        dp[find(x)] = find(y);
        // printf("In unite: %d %d\n", find(x), find(y));
    }
    int find(int x) {
        if (dp[x] == x) 
            return x;
        return dp[x] = find(dp[x]);
    }
    void init() {
        for (int i=0; i<DP_SIZE; i++)
            dp[i] = i;
    }
};

#define ll long long
int main() {
    int n, token=0; scanf("%d", &n);
    vector<pair<int, int>> ps(n);
    map<int, int> xs, ys;
    UnionSet us; us.init();
    for (int i=0; i<n; i++) {
        scanf("%d %d", &ps[i].first, &ps[i].second);
        bool is_x = xs.count(ps[i].first) == 0, 
            is_y = ys.count(ps[i].second) == 0;
        if (is_x)
            xs[ps[i].first] = token;
        if (is_y)
            ys[ps[i].second] = token;
        token += is_x | is_y;
        // printf("Uniting: %d %d\n", ps[i].first, ps[i].second);
        us.unite(xs[ps[i].first], ys[ps[i].second]);
        // assert(us.find(xs[ps[i].first]) == us.find(ys[ps[i].second])); // !
        // printf("After: %d %d\n", us.find(ps[i].first), us.find(ps[i].second));
    }
    set<int> tokens;
    for (int i=0; i<n; i++) {
        auto [x, y] = ps[i];
        // printf("Out: %d %d\n", us.find(xs[x]), us.find(ys[y]));
        // assert(us.find(x) == us.find(y));
        tokens.insert(us.find(xs[x]));
    }
    int group_cnt = tokens.size();
    printf("%d", group_cnt-1);
    return 0;
}