#include <iostream>
#include <map>

using namespace std;


int main()
{
    int n = 0;

    while (cin >> n) {

	map<pair<int,int>, int> mpi;
	int maxX = 0;
	int maxY = 0;

	for (int i=0; i<n; ++i) {
	    int x, y;
	    cin >> x >> y;
    	    mpi[pair<int, int>(x, y)]=0;
    	    if (x > maxX) maxX = x;
    	    if (y > maxY) maxY = y;
	}

while (true) {

	int max = 0;
	for (auto& pi : mpi) {
//	    cout << "* pi(" << pi.first.first << "," << pi.first.second << ")\n";

	    pair<int, int> p[4];
	    p[0] = pair<int, int>(pi.first.first-1,pi.first.second);
	    p[1] = pair<int, int>(pi.first.first+1,pi.first.second);
	    p[2] = pair<int, int>(pi.first.first,pi.first.second-1);
	    p[3] = pair<int, int>(pi.first.first,pi.first.second+1);

	    for (int q = 0; q < 4; ++q) {
//		cout << "p["<< p[q].first << "," <<  p[q].second << "]\n";
		if (mpi.count(p[q])) {
//			cout << "FUCK U\n";
			pi.second = pi.second + 1;
			if (pi.second > max) max = pi.second;
		}
	    }
	}

	if (!max) break;

	map<pair<int,int>, int>::iterator it = mpi.begin();

	for (; it != mpi.end();) {
//	    cout << "(" << it->first.first << it->first.second << ")" << it->second;
	    if (max && it->second == max) {
		 it = mpi.erase(it);
//		 cout << "x\n";
	    } else { 
		it->second = 0;
		++it;
//		cout << "*\n";
	    }
	}
}

        if (!mpi.size()) {
		cout << ((maxX+1)*(maxY+1))/2 << "\n";
        } else {
		cout << mpi.size() << "\n";
        }
    }
    return 0;
}