#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
vector<tuple<int,int,int>> v;
vector<vector<int>> vec(200020);
int h[200020], w[200020];
bool bo[200020] = { false }, bo1 = false;
int co[200020] = {};
int main() {
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> h[i] >> w[i];
		v.emplace_back(make_tuple(h[i], 0, i));
		v.emplace_back(make_tuple(w[i], 1, i));
	}
	sort(v.begin(), v.end());
	int now = 0;
	for (int i = 0; i < v.size(); i++) {
		if (i != 0 && get<0>(v[i]) != get<0>(v[i - 1])) now++;
		if (!get<1>(v[i])) {
			h[get<2>(v[i])] = now;
		}
		else {
			w[get<2>(v[i])] = now;
		}
	}
	for (int i = 0; i < n; i++) {
		co[h[i]]++;
		co[w[i]]--;
		vec[h[i]].emplace_back(w[i]);
		vec[w[i]].emplace_back(h[i]);
	}
	for (int i = 0; i <= now; i++) {
		if (!bo[i]) {
			if (bo1) {
				cout << 0 << endl;
				return 0;
			}
			bo1 = true;
			queue<int> que;
			bo[i] = true;
			que.push(i);
			while (!que.empty()) {
				int m = que.front();
				que.pop();
				for (int j = 0; j < vec[m].size(); j++) {
					if (!bo[vec[m][j]]) {
						bo[vec[m][j]] = true;
						que.push(vec[m][j]);
					}
				}
			}
		}
	}
	int a = 0, b = 0, c = 0, d = 0;
	for (int i = 0; i <= now; i++) {
		if (co[i] == 0) {
			a++;
		}
		else if (co[i] == 1) {
			b++;
		}
		else if (co[i] == -1) {
			c++;
		}
		else {
			d++;
		}
	}
	if (d != 0) {
		cout << 0 << endl;
	}
	else {
		if (b == 1 && c == 1) {
			cout << 1 << endl;
		}
		else {
			cout << now + 1 << endl;
		}
	}
}