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

template <class T>
ostream& operator<<(ostream& out, const vector<T> &cont) {
    out << "[";
    for(const auto &x: cont) out << x<< ", ";
    out << "]";
    return out;
}

#define dmp(x) cerr << #x << " = " << x << endl
#define dmpn(x) cerr << #x << " = " << x <<"; "

#define ff first
#define ss second
#define all(x) begin(x), end(x)
#define sz(x) (int) (x).size()
#define int long long

typedef long long ll;
typedef pair<int, int> pii;
typedef long double ld;


void solve() {
    int N;
    cin >> N;
    map<int, vector<int>> columns;
    for (int i = 0; i < N; i++) {
        int x, y;
        cin >> x >> y;
        columns[x].push_back(y);
    }
    set<int> active;
    int res = 0;
    for (auto kv : columns) {
        bool found_new = false;
        for (int y : columns[kv.ff]) {
            if (active.find(y) == active.end()) {
                found_new = true;
            }
            active.insert(y);
        }
        if (found_new) res++;
    }
    cout << res - 1 << endl;

}

int32_t main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);
    solve();
    return 0;
}