#include<iostream>
#include <string>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

using namespace std;

//重なったら1　そうでなければ0
int check(int loc1[], int loc2[]){
	int kyori =  fabs( sqrt(pow(loc1[0] - loc2[0], 2) + pow(loc1[1] - loc2[1], 2) ) );
	
	//cout << "距離測定:" << loc1[0] << "," << loc1[0] << "と" << loc2[0] << "," << loc2[1] << ":" << kyori << endl;
	if(kyori < 20){
		return 1;
	}
	
	return 0;
}
	
int main(){
	int max;
	int loc[100000][2];
	int count = 0;
	
	
	cin >> max;
	for(int i=0; i<max; i++){
		cin >> loc[i][0];
		cin >> loc[i][1];
	}
	
	for(int i=0; i<max; i++){
		for(int i2=0; i2<i; i2++){
			if(loc[i][0] != -1 && loc[i2][0] != -1){
				if(check(loc[i], loc[i2]) == 1){
					loc[i][0] = -1;
					break;
				}
			}
		}
		
		if(loc[i][0] != -1){
			count ++;
		}
	}
	
	//中身確認
	/*
	for(int i=0; i<max; i++){
		cout << loc[i][0] << "," << loc[i][1] << endl;
	}
	*/
	cout << count << endl;
	
}