#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair< int, int > pii;
typedef vector< int > vi;
typedef vector< vi > vvi;
typedef vector< ll > vl;
typedef vector< vl > vvl;
typedef vector< pii > vp;
typedef vector< vp > vvp;
typedef vector< string > vs;
typedef vector< double > vd;
typedef vector< vd > vvd;

template< class T1, class T2 >
int upmin( T1 &x, T2 v ){
  if( x > v ){
    x = v;
    return 1;
  }
  return 0;
}

template< class T1, class T2 >
int upmax( T1 &x, T2 v ){
  if( x < v ){
    x = v;
    return 1;
  }
  return 0;
}

const int INF = 0x3f3f3f3f;

int N;
vi X, Y;

void init(){
  cin >> N;
  X = Y = vi( N );
  for( int i = 0; i < N; ++i )
    cin >> X[ i ] >> Y[ i ];
}

int cx[ 2000 + 1 ][ 2000 + 1 ];
int cy[ 2000 + 1 ][ 2000 + 1 ];

int eu_dis2( int x, int y, int a, int b ){
  int dtx = x - a;
  int dty = y - b;
  return dtx * dtx + dty * dty;
}

void preprocess(){
  memset( cx, -1, sizeof( cx ) );
  for( int i = 0; i < N; ++i ){
    int x = X[ i ], y = Y[ i ];
    if( cx[ x / 10 ][ y / 10 ] != -1 ) continue;
    int ng = 0;
    for( int dx = -2; dx <= 2; ++dx ){
      for( int dy = -2; dy <= 2; ++dy ){
        int nx = x / 10 + dx;
        int ny = y / 10 + dy;
        if( nx < 0 or nx > 2000 or ny < 0 or ny > 2000 ) continue;
        if( cx[ nx ][ ny ] == -1 ) continue;
        if( eu_dis2( x, y, cx[ nx ][ ny ], cy[ nx ][ ny ] ) >= 400 ) continue;
        ng = 1;
      }
    }
    if( ng ) continue;
    cx[ x / 10 ][ y / 10 ] = x;
    cy[ x / 10 ][ y / 10 ] = y;
  }
}

void solve(){
  int ans = 0;
  for( int i = 0; i <= 2000; ++i )
    for( int j = 0; j <= 2000; ++j )
      ans += cx[ i ][ j ] != -1;
  cout << ans << endl;
}

signed main(){
  ios::sync_with_stdio( 0 );
  init();
  preprocess();
  solve();
  return 0;
}