#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll=int;
using ld=long double;
ld pie=3.141592653589793;
ll inf=144494;
ll mod=1000000007;
int main(){
    ll n;
    cin >>n;
    vector<ll>x(n),y(n);
    for (ll i = 0; i < n; i++)
    {
        cin >> x[i]>> y[i];
    }
    map<pair<ll,ll>,ll>memo;
    ll ans=0;
    for (ll i = 0; i < n; i++)
    {
        bool ok=true;
        for (ll j = max(x[i]-20,0); j <=x[i]+20; j++)
        {
            for (ll k = max(y[i]-20,0); k <=y[i]+20; k++)
            {
                ll z=(x[i]-j)*(x[i]-j)+(y[i]-k)*(y[i]-k);
                if (z<400)
                {
                    if (memo[{j,k}]==1)
                    {
                        ok=false;
                        break;
                    }else{
                        memo.erase({j,k});
                    }
                }
            }
            if (!ok)
            {
                break;
            }
        }
        if (ok)
        {
            memo[{x[i],y[i]}]=1;
            ans+=1;
        }
    }
    cout << ans << endl;
}