/* -*- coding: utf-8 -*-
 *
 * 202.cc: No.202 1円玉投げ - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;
const int MAX_X = 20000;
const int MAX_Y = 20000;
const int DX = 100;
const int DY = 100;
const int MAX_GX = MAX_X / DX;
const int MAX_GY = MAX_Y / DY;
const int RR = 20 * 20;

/* typedef */

struct Pt {
  int x, y;
  Pt() {}
  Pt(int _x, int _y): x(_x), y(_y) {}

  int d2(const Pt &p) const {
    int dx = x - p.x, dy = y - p.y;
    return dx * dx + dy * dy;
  }
};

typedef vector<Pt> vpt;

/* global variables */

Pt pts[MAX_N];
vpt gps[MAX_GY + 1][MAX_GX + 1];

/* subroutines */

/* main */

int main() {
  int n;
  cin >> n;

  int pn = 0;
  for (int i = 0; i < n; i++) {
    Pt p;
    cin >> p.x >> p.y;
    int gpx = p.x / DX, gpy = p.y / DY;
    bool ok = true;

    for (int gy = gpy - 1; ok && gy <= gpy + 1; gy++) {
      if (gy < 0 || gy > MAX_GY) continue;
      for (int gx = gpx - 1; ok && gx <= gpx + 1; gx++) {
	if (gx < 0 || gx > MAX_GX) continue;

	vpt &gv = gps[gy][gx];
	for (vpt::iterator vit = gv.begin(); vit != gv.end(); vit++)
	  if (p.d2(*vit) < RR) ok = false;
      }
    }

    if (ok) {
      pn++;
      gps[gpy][gpx].push_back(p);
    }
  }

  printf("%d\n", pn);
  return 0;
}