#import<bits/stdc++.h>
using namespace std;int x,y;main(){set<pair<int,int>>a;for(cin>>x;cin>>x>>y;)for(auto i=a.lower_bound({x-20,0}),j=a.upper_bound({x+40,0});(i==j?a.emplace(x,y),0:1)&&hypot(x-i->first,y-i->second)>=20;++i);cout<<a.size();}