#import<bits/stdc++.h>
#define F(i,a,x)for(auto i=a.lower_bound(x-20);i!=a.upper_bound(x+40);++i)
using namespace std;int x,y,f,r;main(){map<int,set<int>>a;for(cin>>x;cin>>x>>y;f=!f?a[x].insert(y),!++r:0)F(i,a,x)F(j,i->second,y)f|=hypot(x-i->first,y-*j)<20;cout<<r<<endl;}