#include<iostream>
#include<set>
using namespace std;
int main(){
   int N;
   cin >>N;
   int ans =0;
   set<pair<int,int> > S;
   for( int i = 0 ; i <N; i++){
      pair<int,int> p;
      cin >> p.first>>p.second;
      if(S.size()==0|| S.find(p)==S.end()){
         ans++;
         for( int j=-20;j<=+20;j++){
            for( int k=-20;k<=+20;k++){
               if(j*j+k*k>=20*20) continue;
               //cout << p.first+j<<","<<p.second+k<<endl;
               S.insert(make_pair(p.first+j,p.second+k));
            }
         }
      }
   }
   cout << ans<<endl;
   return 0;
}