#include <bits/stdc++.h>
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define FORR(i,a,b) for (int i=(a);i>=(b);i--)
#define pb push_back

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef set<int> si;
const int inf = 1e9;
const int mod = 1e9+7;

map<pii, pii> m;
int co = 0;
void put(int x, int y){
  int _x, _y, __x, __y;
  _x = x / 10;
  _y = y / 10;
  pii t, t2;
  FOR(i, -2, 3)FOR(j, -2, 3){
    t = pii(_x + i, _y + j);
    if(m.find(t) == m.end())continue;
    t = m[t];
    if( (t.first - x)*(t.first - x) + (t.second - y)*(t.second - y) < 400 )return;
  }
  co++;
  m[pii(_x, _y)] = pii(x, y);
  return;
}
main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  FOR(i, 0, n){
    int x, y, _x, _y;
    cin >> x >> y;
    put(x, y);
  }
  cout << co << endl;
  return 0;
}