#include <bits/stdc++.h>
using namespace std;
#define all(c) (c).begin(),(c).end()
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define REP(i,m,n) for(int i=(int)(m);i<(int)(n);i++)
#define rep(i,n) REP(i,0,n)
#define iter(c) __typeof((c).begin())
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
#define pb(a) push_back(a)
#define pr(a) cout<<(a)<<endl
#define PR(a,b) cout<<(a)<<" "<<(b)<<endl
#define R cin>>
#define F first
#define S second
#define ll long long
bool check(int n,int m,int x,int y){return x>=0&&x<n&&y>=0&&y<m;}
const ll MAX=1000000007,MAXL=1LL<<60,dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
typedef pair<double,double> P;

map<P,int> m;

double D(double x1, double y1, double x2, double y2) {
  return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

int main() {
  int n;
  cin >> n;
  int ans=0;
  int v[20001];
  memset(v,0,sizeof(v));
  rep(i,n) {
    int x,y;
    cin >> x >> y;
    bool ck=true;
    REP(j,-20,21) {
      if(x-j<0 || !v[x-j]) continue;
      REP(k,-20,21) {
        if(m[P(x-j,y-k)]==1 && D(x-j,y-k,x,y)<20) {
          ck=false;
          break;
        }
      }
    }
    if(ck) {
      m[P(x,y)]=1;
      v[x]=1;
      ans++;
    }
  }
  cout << ans << endl;
  return 0;
}