#include <bits/stdc++.h>

#define REP(i, n) for(int i = 0 ; i< (int)n; ++i)

using namespace std;

struct V
{
	int x;
	int y;
	bool visited;
	bool part;
	vector<int> edges;
	vector<bool> matched;
};

bool dfs(vector<int>& path, vector<V>& vs)
{
/*
	for(auto& x : path)
		cerr << x << " ";
	cerr << endl;
	*/
	int from = path[path.size()-1];
	if(vs[from].visited)
		return false;
	vs[from].visited = true;
	bool found = false;
	for(int i = 0; i < vs[from].edges.size(); i++)
	{
		if(vs[from].matched[i] != vs[from].part)
		{
			found = true;
			path.push_back(vs[from].edges[i]);
			if(dfs(path, vs))
				return true;
			path.pop_back();
		}
	}
	if(!vs[from].part && !found)
		return true;
	return false;
}

bool testcase(){
	int n;

	if(!(cin >> n))return false;
	
	vector<V> vs;

	for(int i = 0; i < n; i++)
	{
		int x, y;
		cin >> x >> y;
		vs.push_back(V{x, y, false});
		for(int j = 0; j < i; j++)
		{
			if(abs(vs[j].x - vs[i].x) + abs(vs[j].y - vs[i].y) == 1)
			{
				vs[i].edges.push_back(j);
				vs[j].edges.push_back(i);
			}
		}
	}

	vector<int> left;
	vector<int> right;

	stack<int> s;
	s.push(0);
	vs[0].part = true;
	while(!s.empty())
	{
		auto id = s.top();
		s.pop();
		if(vs[id].visited)
			continue;
		vs[id].visited = true;
		for(auto& n : vs[id].edges)
		{
			vs[n].part = !vs[id].part;
			s.push(n);
		}
	}

/*
	for(auto& v : vs)
	{
		cerr << "(" << v.x << "," << v.y << ") " << v.part << " | ";
		for(auto& i : v.edges)
			cerr << "(" << vs[i].x << "," << vs[i].y << ") ";
		cerr << endl;
	}	
*/

	for(auto& v : vs)
		v.matched.resize(v.edges.size());
	
	while(true)
	{
		for(auto& v : vs) v.visited = false;	
		bool found = false;
		vector<int> path;
		for(int i = 0; i < n && !found; i++)
		{
			bool isFree = true;
			for(auto m : vs[i].matched)
				if(m) isFree = false;
			if(!isFree)
				 continue;
			if(vs[i].part)
			{
				path.push_back(i);
				if(dfs(path, vs))
				{
					found = true;
					break;
				}
				path.pop_back();
			}
		}
		if(!found)
			break;
		for(int i = 0; i < path.size() - 1; i++)
		{
			int u = path[i];
			int v = path[i + 1];
			for(int j = 0; j < vs[u].edges.size(); j++)
				if(vs[u].edges[j] == v)
					vs[u].matched[j] = !vs[u].matched[j];
			for(int j = 0; j < vs[v].edges.size(); j++)
				if(vs[v].edges[j] == u)
					vs[v].matched[j] = !vs[v].matched[j];
		}
	}

//	cerr << "matching:\n";
/*
	for(int i = 0; i < n; i++)
		for(int j = 0; j < vs[i].edges.size(); j++)
			if(vs[i].edges[j] < i)
				std::cerr << "(" << vs[i].x << "," << vs[i].y << ") (" << vs[vs[i].edges[j]].x << "," << vs[vs[i].edges[j]].y << ")" << vs[i].matched[j] << endl;
*/
	int result = n;
	for(int i = 0; i < n; i++)
		for(int j = 0; j < vs[i].edges.size(); j++)
			if(vs[i].edges[j] < i && vs[i].matched[j])
				result--;
	cout << result << endl;
	return true;
}


int main(){
	while(testcase());
	return 0;
}