#import<bits/stdc++.h>
using namespace std;int x,y,r;main(){set<pair<int,int>>a;auto i=end(a),j=i;for(cin>>x;cin>>x>>y;i==j&&(a.emplace(x,y),++r))for(i=a.lower_bound({x-20,y-20}),j=a.upper_bound({x+40,y+40});i!=j&&hypot(x-i->first,y-i->second)>=20;++i);cout<<r;}