#include <algorithm>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <sstream>
#include <functional>
#include <map>
#include <string>
#include <cstring>
#include <vector>
#include <queue>
#include <stack>
#include <deque>
#include <set>
#include <list>
#include <numeric>
using namespace std;
const double PI = 3.14159265358979323846;
const double EPS = 1e-12;
const int INF = 1<<25;
typedef pair<int,int> P;
typedef long long ll;
typedef unsigned long long ull;
#define N 20050
int n;
set<int> st[N];

bool check(int x, int y){
	for(int i = -20; i <= 20; i++){
		for(int j = -20; j <= 20; j++){
			if(i*i+j*j>=400) continue;
			if(st[x+i].count(y+j)) return true;
		}
	}
	return false;
}

int main(){
	cin>>n;
	int res = 0;
	for(int i = 0; i < n; i++){
		int x, y;
		cin>>x>>y;
		x += 20;
		y += 20;
		if(check(x, y)) continue;
		res++;
		st[x].insert(y);
	}
	cout<<res<<endl;
	return 0;
}