#include<sstream>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<numeric>
#include<functional>
#include<algorithm>
using namespace std;
#define INF (1<<29)
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define all(v) v.begin(),v.end()
#define uniq(v) v.erase(unique(all(v)),v.end())
#define indexOf(v,x) (find(all(v),x)-v.begin())



int highest_pop(unsigned int b){
#ifdef __GNUC__
	return 31-__builtin_clz(b);
#else 
	int res=0;
	for(int i=4;i>=0;i--){
		int shift=1<<i;
		if(b>>shift){
			b>>=shift;
			res|=shift;
		}
	}
	return res;
#endif
}


template<int U=20> 
class Set{
	unsigned int summary;
	Set<U-5> ch[1<<5];
	static int low_bits(unsigned int a){
		return a&((1<<U-5)-1);
	}
	static int high_bits(unsigned int a){
		return a>>(U-5);
	}
	static int index(unsigned int high,unsigned int low){
		return high<<U-5|low;
	}
public:
	Set():summary(0){}
	~Set(){}
	void clear(){
		for(int i=0;i<(1<<5);i++)
			if(summary>>i&1)ch[i].clear();
		summary=0;
	}
	void insert(int v){
		int high=high_bits(v);
		summary|=1<<high;
		ch[high].insert(low_bits(v));
	}
	bool erase(int v){
		int high=high_bits(v);
		if(!(summary>>high&1))return true;
		if(!ch[high].erase(low_bits(v))){	
			return summary&=~(1<<high);
		}
		return true;
	}
	int nextvalue(int v)const{
		int high=high_bits(v);
		int low=low_bits(v);
		int a;
		if((summary>>high&1) && (a=ch[high].nextvalue(low))!=-1){
			return index(high,a);
		}else{
			high=summary&~((1<<high)-1)&~(1<<high);
			if(!high)return -1;
			high=highest_pop(high&-high);
			return index(high,ch[high].min());
		}
	}
	int prevvalue(int v)const{
		int high=high_bits(v);
		int low=low_bits(v);
		int a;
		if((summary>>high&1) && (a=ch[high].prevvalue(low))!=-1){
			return index(high,a);
		}else{
			high=summary&((1<<high)-1);
			if(!high)return -1;
			high=highest_pop(high);
			return index(high,ch[high].max());
		}
	}
	int min()const{
		if(!summary)return -1;
		int high=highest_pop(summary&-summary);
		return index(high,ch[high].min());
	}
	int max()const{
		if(!summary)return -1;
		int high=highest_pop(summary);
		return index(high,ch[high].max());
	}
	bool member(int v)const{
		int high=high_bits(v);
		return (summary>>high&1) && ch[high].member(low_bits(v));
	}
};


template<> 
class Set<5>{
	unsigned int summary;
public:
	Set():summary(0){}
	void clear(){summary=0;}
	void insert(int v){
		summary|=1<<v;
	}
	bool erase(int v){
		return summary&=~(1<<v);
	}
	int nextvalue(int v)const{
		int a=summary&~((1<<v)-1)&~(1<<v);
		if(!a)return -1;
		return highest_pop(a&-a);
	}
	int prevvalue(int v)const{
		int a=summary&((1<<v)-1);
		if(!a)return -1;
		return highest_pop(a);
	}
	int min()const{
		if(!summary)return -1;
		return highest_pop(summary&-summary);
	}
	int max()const{
		if(!summary)return -1;
		return highest_pop(summary);
	}
	bool member(int v)const{
		return summary>>v&1;
	}
};




Set<15> xset[20021];


int main(){
	int n,ans=0;
	cin>>n;
	rep(i,n){
		bool hit=false;
		int x,y;
		cin>>x>>y;
		for(int a=max(0,y-20);!hit&&a<y+20;a++){
			int b;
			b=xset[a].nextvalue(x);
			if(b!=-1&&(a-y)*(a-y)+(b-x)*(b-x)<20*20)hit=true;
			b=xset[a].prevvalue(x+1);
			if(b!=-1&&(a-y)*(a-y)+(b-x)*(b-x)<20*20)hit=true;
		}
		if(!hit){
			xset[y].insert(x);
			ans++;
		}
	}
	cout<<ans<<endl;
	return 0;
}