#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <climits>
#include <vector>
#include <numeric>
#include <complex>
#include <map>
#include <bitset>
#include <utility>
using namespace std;

//#define __int64 long long
#define long __int64
#define REP(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)
const int Vecy[4] = {0,-1,0,1};
const int Vecx[4] = {1,0,-1,0};

const int Xy = 20000;
const int Pat = 100;
const int Kazu = Xy / Pat;
vector<vector<vector<pair<int,int> > > > field;
	
bool check(int testy, int testx){
	int fy = min(Kazu - 1, testy / Pat);
	int fx = min(Kazu - 1, testx / Pat);
	int kyori;
	
	for(int iy=max(0,fy-1); iy<=min(Kazu-1,fy+1); iy++){
		for(int ix=max(0,fx-1); ix<=min(Kazu-1, fx+1); ix++){
			for(int i=0; i<field[iy][ix].size(); i++){
				kyori = pow(testy - field[iy][ix][i].first , 2) + pow(testx - field[iy][ix][i].second , 2) + 0.2;
				if(kyori < 400){
					return false;
				}
			}
		}
	}
	
	//データ追加
	field[fy][fx].push_back(make_pair(testy, testx));
	
	return true;
}

int main(){
	int n;
	int ans = 0;
	int y,x;
	
	//vector
	field = vector<vector<vector<pair<int,int> > > >(Kazu, vector<vector<pair<int,int> > >(Kazu, vector<pair<int,int> >()));
	
	cin >> n;
	rep(i,n){
		cin >> x >> y;
		if(check(y,x)){
			ans ++;
		}
	}
	
	cout << ans << endl;
    
    return 0;
}