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

int sy[20030];
int sx[20030];

int main() {
	int N;
	cin >> N;
	vector<unsigned int> x(N), y(N);

	for (int i = 0; i < 20030; i++)
	{
		sy[i] = 100030;
		sx[i] = 100030;
	}

	for (int i = 0; i < N; i++)
	{
		cin >> x[i] >> y[i];
		sy[y[i]] = min(sy[y[i]], i + 1);
		sx[x[i]] = min(sx[x[i]], i + 1);
	}

	int ans = 0;
	set<unsigned int> s;

	for (int i = 0; i < N; i++)
	{
		bool flag = true;
		for (int dy = -20; dy <= 20 && flag; dy++)
		{
			for (int dx = -20; dx <= 20 && flag; dx++)
			{
				if (dy*dy + dx*dx >= 400) continue;
				int Y = y[i] + dy;
				int X = x[i] + dx;
				if (sy[Y] >= i + 1 && sx[X] >= i + 1) continue;
				if (s.count(Y * 20001 + X)){
					flag = false;
					break;
				}
			}
		}
		if (flag){
			ans++;
			s.insert(y[i] * 20001 + x[i]);
		}
	}
	cout << ans << endl;
	
}